For The Elder Scrolls V: Skyrim (Special Edition & Anniversary Edition)
I strongly recommend using a mod manager for installations, as it's ideal for long-term management, proper load order, and easier troubleshooting.
Manual installation is also possible by extracting the files into the game's Data folder. Always read the included instructions.
For Elden Ring
Install using ModEngine 2 or the mod loader specified in the included instructions. Carefully follow the setup steps provided with each mod.