Another alternative way to patch the hole if they're the size of an electrical receptacle or smaller..
Measure the hole and say it is 3" wide by 4" high get a piece of drywall that is 5" wide by 6" high.
Measure and mark out the hole on to the back of the drywall piece.
Score/Cut from the back of the piece around the marking and make sure not to puncture the drywall paper on front.
Pull off the drywall so you have the patch for the hole with the extra 1" perimeter of paper. This paper will be used as the tape and will help hold the drywall in place. The paper may curl slightly depending on how long it is around the border, which you can trim, but the compound/mud will keep it flat during install.
Get out your drywall compound/mud apply some to the wall or drywall piece and slid in to place. Apply your first coat lightly to reduce amount of sanding and apply 2,3 4 coats as needed.
I've used this technique numerous times in my bassment due to wire runs and it works really well. I'm not a trade man and taught myself to do drywall mudding repairs after watching many people doing it. The main thing is patience and not to overwork the compound/mud. Light coats will make sanding easier, and sanding will make your patch look good. Don't worry too much on how it looks the first couple coats until sanded.
It took me about 4 patches to get used to the idea of not making it look perfect while applying the compound/mud. Good luck.
