Once the support piece is sufficiently secured (whether you glue it or screw it) you're ready to fit a piece of drywall for the hole. Make sure that you are using the same thickness of drywall that is already installed. Cut the piece so that it is a fairly good match. You don't want 1/4" gaps all around. An 1/8" is MAX.

Applying Your First Coat

Finishing drywall is an art. If this is your first time, don't expect to have a finished product that is perfect. If the wall is textured, getting the repair to go un-noticed is almost impossible, but if the wall is smooth, you'll have an easier time of it.

Applying the Second Coat

With the first coat completely dry and any ridges knocked down, you can get ready to apply the second coat. This coat will be a little thicker than the first coat. You want to try to completely cover the tape and the surrounding area. Use a wider knife like an 8". Apply it and then wipe it smooth. Try to feather into the existing wall. This is an art. Sometimes it is beneficial to press on the knife so that one side is in contact with the wall and the other side is 'floating' over the patch.

Adding Support for the Patch

What we're gonna do is install an actual piece of drywall to fill our void. With big holes, you can't just fill it in with mud. Don't waste your time with a 'patch kit' on a 6 inch wide hole. It'll just crack later and you'll have to do it all over again.

Sizing Up The Hole

Accidents happen. One of the most common ones is a nice sized object slamming into your drywall

and leaving not a dent, but an actual void. When drywall is hit with enough force (and especially by a smaller object like a fist, broom stick, or childs head) in between studs, you'll be left with a nice size hole that can't just be 'patched'.