The row of controls at the top of the screen can be swiped left and right to reveal more controls. Certain controls can also be tapped or pressed and held to reveal more options.
Be sure to try the "audible for" controls. These silence the metronome for a certain number of bars, leaving it up to you to maintain your tempo during the silences.
The add subdivision button opens a screen where you can choose to add a new subdivision from any of three different categories: common, custom, and presets. Using custom subdivisions, you can create practically any rhythm you want, from quarter notes to 7/13 tuplets.