We're still figuring out exactly how we want that to work in the new design. There aren't individual item pages anymore, you interact with the set instead. You can still use the free assets by searching for them in the in-app search -- and once you find them there, star them to add them to Your LIbrary where you can add tags to them. That said, the next update is going to include a major overhaul to the Your Library feature, and one of the things we'll be looking into is how to make it easier to integrate things you upload, things you've bought, and things that are built-in together to a cohesive "Your Library" interface. If searching in-app isn't working, let us know and we'll see if we can get something temporary put in place between now and then.
