NMM
1. Download with NMM or download manually then add mod from file.
2. Install.

Manual
1. Download manually.
2. Extract the 7z file and its contents.
3. Drag contents into SkyrimData and merge/overwrite when prompted.
4. Enable BOTH amethysthollowsmaster.esm AND amethysthollowsupdate.esp.




Uninstall procedure:

First and foremost, remove anything from the Amethyst Hollows area that you want to keep (uninstalling will cause all of those items to vanish), including any followers you have “relaxing” in the area.

Exit the area into a safe location, such as a vanilla exterior in Skyrim. Save your game. Quit Skyrim.


NMM
Uninstalling with NMM is very easy. Simply deactivate the mod under the Mods tab. NMM will automatically remove all traces of the mod from your skyrim data folder.


Manual
Manual uninstall is a bit more tedious, but it is extremely important that you delete ALL loose files associated with the mod, especially the scripts, which will continue to run even if the esp and esm are disabled or deleted.

1. Delete both AmethystHollowsMaster.esm and AmethystHollowsUpdate.esp. from the data folder

2. Open meshes folder and delete the following folder and all its contents:
dcvrworks/amethyst
actors/character/facegendata/facegeom/amethysthollowsmaster.esm

3. Open textures folder and delete the following folder and all its contents:
dcvrworks/amethyst
actors/character/facegendata/facetint/amethysthollowsmaster.esm

4. Open sound folder and delete the following folder and all its contents:
voice/amethysthollowsupdate.esp

5. Open scripts folder and delete the following .pex files:
ALL files starting with DCVR_AH_
ALL files starting with DCVR_PF_AH_
ALL files starting with DCVR_QF_AH_
ALL files starting with DCVR_TIF__0300 (make sure to only delete the ones with numeric values starting with 03 and not 01 or 02 if any, because those belong to Black Tower, my other mod)

6. Open the Source folder inside the Scripts folder and delete the .psc files of the same name from step 5.