How to safely install mods in Skyrim

First thing you gotta do is download a mod manager like Mod Organizer 2 or Vortex, they keep everything organized without touching the game's base files, that's crucial. Then look for mods on Nexus Mods, it's the most reliable community, read the comments and requirements before installing anything because some mods need specific dependencies. I always make a backup of my Skyrim folder before I start messing with it, and start with just a few mods to see which ones work well together, because throwing 300 mods in without testing is a recipe for everything to go to shit. Oh, and disable broken mod scripts from the game menu if you see something breaks, that's basic stuff to avoid crashes.

What they say about using a manager is fine, but I'd add that before you install anything you should back up your Skyrim folder. And even if you use Mod Organizer 2 or Vortex, always read the comments on Nexus because there are mods that don't play well together - I've messed up more than once by installing something without checking properly and then the game was a total mess.