How to patch a hole in drywall?

you can purchase 'Dry Wall' paste at any good hard ware store, apply with a putty knife, allow to dry, sand, and paint -- unless the hole is HUGE --- then you may need to cut out the damaged area, patch with another piece of dry wall, cut to fit, tape w/ dry wall tape, sand and paint

Google: "HOw to patch a hole in drywall". You will come up with many U-tube videos that give step by step directions. A small hole requires just some spackle. A large hole is more complicated.

Buy drywall compound in any hardware dept. For smaller hole, use a spatula to spread compound evenly & smoohly, let dry, sand smooth & repeat if needed. If large hole (fist size or more) you may need to secure a piece of plywood behind hole, then cut a piece of drywall the size of opening & screw into plywood, lay mesh tape over that & apply compound over all. For larger holes, use several thin coats - a thick coat slathered on will crack & take longer to dry. Again, sand & repeat. To paint, use primer & then your top coat.

Best answer is to Google it, the patch job is fairly simple but hard to explain.

https://www.lowes.com/projects/repair-and-maintain/patch-and-repair-drywall/project

Start with cutting a square around the hole with a saw used for this purpose .Next, put a screen in place, which you can be purchase at Homedepot, and ask them while your there, how to finish the project. You'll need spackle, and some sandpaper or a sander block.