1. Wherever you see the '♡' symbol on posts and on the applications listed -> see example below. When you select it, the heart turns pick -> see below.
2. They are stored on your favourites page, which you can see when you press the ♡ on the navigation bar on the bottom of the screen. You can see a toggle screen, the application favourites are selected below. All the applications from all the challenges you've done, show here.
3. When you click the Post on the toggle bar, all the posts you've "liked" in all the challenges you've done, show here.