Use a framing square to mark a perfect square on the wall around the damaged area. It doesn’t matter how large the square is as long as it encompasses all damaged or cracked drywall. Using a utility knife, score along the outline to remove the drywall square with all damaged areas.
Apply a layer of joint compound around the edges of the patch and slide it into place. Using a putty knife, add a layer of joint compound around the seams of the patch, making sure to fill the gaps. Let dry overnight.
Sand the joint compound until it is level and flush with surrounding drywall. If the compound shrank or is uneven, it may be necessary to apply another coat of compound. When dry, sanded and smooth, paint the drywall.