To choose your favorite teams for your My Action profile, from the My Action tab, click on the gear icon in the top right corner to open the app's Settings. Then, click on Favorite Teams.
From here, you can add teams by clicking "+ Add Team" or remove teams from your favorites by clicking the Edit option in the top right corner.
After you have edited your favorite teams, exit the page by clicking the arrow in the top left corner, and your teams will be saved.