When you first access The Church App, you will be walked through adding your Home Church. If you access The Church App for the first time at your church, you'll be prompted to open directly to your church's content!
However, if you move or want to add other churches as Favorites, you will go through the side menu (☰), and Explore. Here you can view your Home church and Favorites, and click the magnifying glass to search for another church.
Once you're on a looking at a church's content, you can click the kebab menu button (⋮) in the top right to either set the app as Home or a Favorite. If need be, you can remove an app from your favorites following these same steps.