The trigger guard has one punch pin and one push pin.  The punch pin is by the grip.  You take a punch and hammer it out, then you push the push pin in and the trigger guard drops off.

There should be some sort of screw or allen head underneath the grip.  Unscrew and remove.  There will be a spring and safety detent you need to watch out for.  Put it back the same way it came out.  

It's about the simplest job you can do on an AR.  

Quoted: Make sure when you drive the back roll pin out that you support the ear of the receiver on a hard block with a hole in it for where the pin needs to fall out. Not doing so you will break the ear off your receiver and be pissed at yourself.