Guess left without paying.

1) Hi, I'm new to booking and by mistake I set up cash in pay during the onboarding, but I wanted to change to accept credit card only. (I did in my other listing) I can't find where to change from cash only to Credit card only. Please help. 

2) One person booked, (believing that was charged to CC), and then I find out it was set-up as cash. 
The guest left without paying. 
PLEASE HELP. How can I charge my guest after checkout?