Beginner stymied from the beginning

The features look pretty cool and probably would be for a more advanced musician. I’m close to a beginner so possibly I’m missing something obvious but the first thing I wanted to do was play a song in 6/8. I cannot for the life of me figure out how to set the beat to eighth note. Am I supposed to double the tempo and use quarters?

The metronome feature on Guitar Tuna lets you set a time signature so I assume this is a common function.

I tried emailing for support but the email bounces

pleaseletthisnicknamebeavailab about Metronomics HD, v1.2