If you don't really know what you're doing with modding or it's your first time, I would highly suggest looking at some videos that describe the process and walk you through on how to do it. Modding is a very tricky aspect of PC gaming and in order for things to come out right, you need to be fairly strict on how you set up your mods and preferences. You're basically editing the games core files when you mod, so any information on keeping your game backed up and proper installation are undoubtedly necessary.