Yes, it's rather wordy, but make sure you read it all through once before following it. Guide has 'CBBE' as the default body as that is what I use. See the mod description for other compatible body mods. Scroll to the bottom if you just want to know about the in-game sliders.
1. Install BodySlide according to the installation instructions for your mod manager (see mod description).
2. Install CBBE and the body/outfit BodySlide files that come with it. Installation instructions are in its description.
a. (Optional) Install other BodySlide-compatible outfit mods if you want them to fit your preset (Check CBBE mod list).
3. Launch BodySlide. Go to Skyrim Special Edition/Data/CalienteTools/BodySlide. Double-click on BodySlide.exe/BodySlide x64.exe to open the utility. If using Vortex, you should also open from this location through your manager.
4. At the top, in 'Outfit/Body' select one of the bodies. CBBE Body/CBBE Body Physics/CBBE Body Special are 'nude'. The CBBE NeverNude/CBBE Underwear bodies have underwear meshes covering all nudity. Ensure you have installed XPMSSE if you use the CBBE Body Physics/Special body.
5. In the 'Preset' dropdown, select a preset, or leave it as it is and simply start moving the sliders around. Low-weight is the body at '0' in the in-game weight slider, while high weight is at '100'. You can type numbers into the boxes if you want to use negatives (put in a - before the number) or go over 100%, but going outside the 0-100 range is not recommended as it can cause distortions or bad clipping with outfits. If you have a shape in mind, it's usually a good idea to start with a preset closest to your desired shape.
6. Click on 'Preview' at the bottom to open the preview window. The mesh shape will change as you move/edit sliders. The bar at the top of the preview window reflects the shape you'll get with the in-game weight slider. You can right-click-and-drag the model to rotate it, and left-click-and-drag to move it around the window without rotating. Scroll-wheel to zoom also works.
7. Once you're happy, click on 'Save As' next to the Preset drop-down. 'Save' will overwrite the current preset selected. Warning: You can not 'undo' Save. If you Save by accident, you will need to reinstall the original preset file/you will lose the original preset if it has no backups.
8. Type in a name for your preset in the box that pops up, and check the boxes for what 'groups' you want your preset to appear in. Always select the 'CBBE' group so it appears for all installed compatible outfits.
9. Click Save. BodySlide will open a window to the BodySlide/SliderPresets directory. Click Save again. You preset will now appear in the 'Preset' drop-down menu.
b. (Optional) If your aim is realism and you made a nude body with gravity, make a second preset just for outfits/NeverNude/Underwear, removing any/most gravity from your 'nude' preset, and applying cleavage/pushup/flatness etc. You can look at the 'CBBE Slim (Outfit)' and 'CBBE Curvy (Outfit)' presets made available for all underwear and clothing styles for ideas to make it look realistic for both small and large breast sizes, respectively.
10. (Only one preset? Skip to 11) With CBBE Body/Body Physics/Special selected in the 'Outfit/Body'drop-down menu, and your preset selected in the 'Preset' drop-down, click on Build. This will automatically install the unclothed nude body meshes. Make sure you have at least XPMSSE installed if you use the Physics or Special body.
c. (Optional) If you made edits to the wrist/ankle sliders, be sure to build CBBE Feet/Hands/Hands Beast with your preset selected as well.
d. (Optional) If you have a lot of outfit mods installed, and/or only want to see/build meshes for certain ones (such as physics-only meshes), you can use the GroupFilter and OutfitFilter options at the top of BodySlide to narrow down the selection. Just click on the magnifying glass, 'Choose Groups', and select what you want. Again, only what is selected will have the option to build meshes for them. Leaving these Filters alone will mean you have the option to build everything.
11. With your (outfit) preset selected, click on BatchBuild. This will allow you to generate multiple meshes instead of the single one that Build creates (just as it says when you hover over it). Uncheck anything you don't want built (e.g. if you did step 10 above, you don't want/need CBBE Body/Body Physics). You can right-click this window and choose to Select all/none/invert select if desired. Do not build any Physics meshes if you don't have at least XPMSSE installed. Note that if there are two or more options for a certain body/outfit (e.g. CBBE Body/Physics/NeverNude/Underwear all change the same thing, the in-game unclothed body), you will get another window listing these meshes to select which options you want generated.
12. Click Build. BodySlide will automatically install the outfit meshes into the correct directories.
Now the outfits will be the shape of your preset.
Note: Pay attention to the tool-tips. If you CTRL+Click the Build button, the meshes will generate inside the BodySlide folder. If you CTRL+Click the BatchBuild button, you can choose a directory to install all of the meshes you generate. You will most likely need to utilise this if you are using a custom race and need to install meshes manually.
In-game sliders/RaceMenu Morphs: When installing CBBE, you will have an option for 'RaceMenu Morphs'. This allows you to use the BodySlide sliders in-game for your player character only, using RaceMenu, and the RaceMenuMorphs.esp. But, this still requires some use of BodySlide; open BodySlide, select a body/outfit and preset (which NPCs will use, and which will be the starting point of your in-game preset), check the 'Build Morphs' box at the bottom of the BodySlide window, and then use the Batch Build option/button to generate all meshes.
