Adding Mixes to Favorites

How do I add Mixes to my favorites list? I've been trying to figure this out for about a year now..

the other day, completely by fluke, I was able to add a Mix to my favorites list.. now I can't figure out how I opened the Mix in order to click the heart to add to favourites..

usually when I touch a Mix it won't open up, it just starts playing, it won't let you see the songs in the list, only the song that's currently playing

I don't have a computer, so everything I do on this app is done on my android, so please don't suggest I use a desktop.