ok, so i had it attached with bolts and nuts on the back... i had waited to take my rear bumper off to install this frame cuz i didnt know how to get a nut on the backside, but today i noticed somehow one of the bolts came out and its hanging by one side.
is there a way i can secure this thing without taking my bumper off again?

 

When I swapped out my license plate frame the other day, there were U-Nuts on mine. That would be the best bet for you. This way you don't have to worry about the nuts falling out if you take your license plate off again. They don't cost much, but I'm not sure where you can get them from. I found a few vendors on Google.

http://www.thread-rite.com/itw_shakeproof/unuts_1.htm

http://www.northlandfasteners.com/catalog/db6.html

 

Not sure why you would have to use a basic nut. Your bumper should have come attached with clip nuts on the bumper itself. Then you just screw the bolt through the license plate/frame and into the clip nuts.

Something like this