You can change the time signature using the metronome bar and beat tap keys, located in the Drummer Control mode.
To change the time signature to 7/4, first press the bar tap key, followed by the beat tap key 6 times, followed by the bar tap key again.
To change to 3/4 for example, you would press the bar tap key, followed by the beat tap key twice, followed by the bar tap key again.
To display the current time signature and metronome tempo, you can browse the metronome (the key for this is found in the 'Drummer Volume Control mode' - please refer to the Quick Reference Guide for more information).