The metronome is your best friend when you need to play in a steady tempo, or when you need a count-in to the part you're playing next.
When you enter the studio, the metronome is enabled by default (unless you add a loop - then it's disabled). It can be enabled/disabled by clicking the ON/OFF button (1) at lower-right corner of the studio. You can also change the volume and sound for the metronome if you click the cog wheel next to the ON/OFF button!
To the left of the metronome ON/OFF button, you will find the Tempo (2). This is where you set the tempo of your project in BPM (beats per minute). The default tempo when you start a new project is 120 BPM, which means that for every minute, you will hear 120 beats. Entering a higher value here results in a faster tempo, and vice versa.
(1) Metronome ON/OFF button