After the game has been setup, you can start entering the scores. In the score entry view, just press on the green hole indicator next to the right player's name, and enter his/her score on that particular hole. The application will do all the calculation for you so just enter the score as it is. The scores will update after each entered results.
On iOS: Find the score entry view by turning the device to landscape mode, leaderboards can be viewed in portrait mode.