Custom Sims not appearing in the library?

Hey,

I tried installing this sim: http://www.thesimsresource.com/downloads/details/category/sims4-sims-female-youngadult/title/sophia-johnson/id/1298723/

I put the files in my "Tray" folder as I am supposed to but I can't find the model in game...

I'm using Sims 4 downloaded and installed according to this guide.

I also tried downloading a different model but still no go. What am I missing?

If you open your library, select 'households' on the left, and then, further down click on 'Advanced' (...) and then enable 'include custom content' your sim should show up in the window on the right.