@Riini16233 , first thing to do is to locate your Library folder (which is hidden on a Mac) and create a Download folder. I've copied that particular section and will try to break it down into individual steps.
1) To find your Library folder, click on your Desktop, find the "Go" command at the top in the Finder, hold your cursor button over Go and press the Option key on your keyboard and Library will show when you do that.
2) Scroll through the Library folders until you find one called "com.aspyr.sims2.appstore" and open the folder.
3) You should see two files in there and open the Data File.
4) From there, locate another file named "Library" and then in that file you should should find another Aspyr folder which when opened will reveal the Sims 2 folder (exactly like the original game and on the Windows side).
5) From there check to see if you have a folder named "Downloads" and if you do not, simply create one. This is where all your CC and Mods will be stored.
Once you've done these steps, let me know and we'll continue from there. 🙂