Logic Pro 9 Trouble recording vocals through interface



I am very new to recording with computers, and I'm trying to record vocals. I have my mic going through my usb interface, I have the interface set as the source for the audio for my vocal track, and I have the track record enabled. I can hear sound from the mic, but when I start recording it doesn't record anything. I know that this is my inexperience and I don't have something set up right, but I've searched a lot and watched a bunch of video tutorials and I can't find whatever it is I need to do differently.