Please keep in mind that this has the potential for causing issues in your game if any of these files conflict with game updates. One note of caution I noticed this creator has included a great number of package files across many folders and subfolders. I renamed that folder SimsulaniMods to make it not so confusing. The downloaded folder also contains a 'Mods' folder which needs to be in your Documents / Electronic Arts / The Sims 4 / Mods folder. So, adding the tray files is just one step. This is what I got when I downloaded and extracted the files. Hope this helps but please let us know if you're still having trouble. Did you also add the Mods folder to your Documents / Electronic Arts / The Sims 4 / Mods folder? In order to see the household in your your Library, you'll need to check the box for 'Include Custom Content'. I found them! :-) You said you added the tray files. Information, Guides and Announcements for the EA app.
