If you are new to DiscGolf this screen should be mostly empty since you haven't created any games/scorecards yet.
Follow the instructions on the screen to create a New Game (click the icon on the menubar).
Course + Player(s) = Game
Since you haven't played any games yet you must select your default course. The Select course page displays a list of courses for your region. Your region can be changed in Settings at any time (use this if you travel to another state or country). You can either pick a course from the list of courses or create a new course. You can also select courses in your region on a map to find which course is the closest to your location. Once you select a course you are automatically taken to the Create game screen.
Now that you have selected your course you must also select players. Open the menu to create players from your contacts or add new players manually. You can create as many players as you want. Once your players are created you must select them. Players will be added to the scorecard in the same order you've selected them (first selection will be at the top of the scorecards player list). Once you have selected your players you must click the Disc-icon/Start Game on the menubar to create the Scorecard.
Hold you phone in portrait mode to edit the scorecard. Rotate your phone to landscape mode to view the scorecard overview. There are plenty of features in the scorecard to play around with, you can read more about the Scorecard in the help pages.