So try one first and see how it goes, before dumping stuff in wholesale Remember, if it DOESN'T work, you just have to remove it from the mods folder and everything will be fine. Sometimes just referred to in The Sims community as CC. Get to know this terminology: Custom Content: This is the addition of player-made clothing or objects to the game. Then go back into Sims 4 Studio, merge the remaining files as explained above and then put the new merged. It IS probably worth exercising some caution here no guarantee they'll work in the released game. Learn about the new disable Mods feature, the Maxis policy towards Mods and how to safely re-enable Mods. If you want to use the mods you have from the demo in the game, you'll need to copy them over.
Note that when the full game comes out, it will presumably create a new folder in My Documents.
(You can use one level of subfolders by default if you want more, you'd have to modify the resource.cfg file.) Installing mods in TS4 is far simpler than TS3, since the game comes with a premade mods folder. Why'd you include the warning but not a link to the actual instructions? How To Install Custom Content in The Sims 4