Put in two sister studs then screw in drywall, tape, bed, skim and sand. What i mean by this is take a cut piece of 2x4 or metal stud, screw it to the side of the drywall leaving half of the stud exposed, install pieces you have and screw them to the 2x4 that is showing. now that is is patched back in and secured with screws you can start the mudding. If you do not have it screwed back in you will fight the mudding process the whole time and it will never work. Feel free to PM me for my number and I can probably explain a little better over the phone.