Once you have finished 9 or 18 holes, press the bottom left and right buttons to scroll until you see "End Round". You can press the top right button to end the round. You can then start a new round if you are playing another course.
If you start your round at any other hole than the 1st, and the 18th hole is not your final hole (a shotgun start for example) then there are a number of option for you to choose from for ending your round. This also applies if you would just like to manually end your round at any point.