I bought a double edged razor. I'm scared. Any tips?

[BishBashBoshy]

I think this was probably a bit of a silly thing to do given that I can make a mess of my legs with a normal disposable razor.

I'm particularly concerned about my underarms. I've looked at videos of men shaving their faces but there seems less likelihood of them catching themselves with the other side of the blade than with my underarms. I'm not even thinking about my bikini line at the moment!