How do I change Firing Groups on Oculus Touch?

I am stuck on the first combat tutorial because I cannot activate my secondary weapon. When the second ship attacks me I can look to the right and edit both the first and second firing groups on that display, but when I pull the left trigger, it does not fire anything.

How do I change to my secondary firing group?
 
I should mention that I got the secondary weapon firing one time... but I have not been able to reproduce it. Is there a Touch Control cheatsheet I can view somewhere?
 
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