The 'Favourite' feature in School Stream allows you to save content for later viewing.
You can save content by swiping left and tapping the 'Save' button so that it turns yellow.
You can then find this content by navigating to the menu ( Menu Icon at the top left of the app).
On the menu, select 'Saved'.
This will take you to your Favourites menu, where you should see all your saved content.