#1 question.....has the leak been repaired?? otherwise, total waste of time and cash...
First, repair the leak in the roof, or the pipe that's causing the leak.
It depends how large the damaged area is. You can patch a smaller area using drywall tape, mud and sanding. Then prime and paint to match the existing ceiling.
For a larger hole, you may have to cut a new piece of drywall to patch. Cut the damaged area to a "regular" shape and cut the new piece to fit inside as closely as possible. Attach with drywall screws to the framing. Drywall tape the edges, mud, and sand. Prime and then paint.
Hi Bre: After fixing the leak problem, try this:
Most times you can get scrap pieces of dry wall at your home improvement store free. Just ask if they have any. A no is better than a missed yes:) It's not as hard to do as it seems, even though this looks long, and you can do this for any type of hole in wallboard.
Here's what you need.
A piece of wallboard that is about 3" bigger than your hole,
1piece of string about 3 feet long with a knot at one end
1 piece of wood, like paint stirring sticks, 4" longer than the hole
something to make a small hole in the new wall board and stick
A can of fruit, soup, beans or something, doesn't matter.
Now, the destructions:)
Cut the drywall patch so that it will cover your hole with a couple of inches all around. Now, draw around this piece of drywall, onto your ceiling. Draw an arrow on the patch and on the ceiling itself on the same edge. This way, you will have a perfect fit, knowing which way to put the patch on. Now, cut the old drywall out along the pencil line, and you will have the size of the opening left in it, or at least close. Get the stick and poke a hole in the middle and centre. Run the string through the paint stick with the knot coming out of the back, facing the inside of the hole, and the string hanging on the outside of the ceiling. Make a hole in the middle centre of your new wall board, opposite the holes in the stick. Glue the stick firmly to the inside of the ceiling, gluing at the ends of the stick with about 2 inches sticking over the inside edges. When this is fairly well set, put some spackle on the rough edges of your patch, the stick and the sides of the hole. While that is drying a bit, pull the string through the back of the patch where you made the hole. Pull the string all the way through, noting (ta da!) the position of the arrow! :), and push the patch into the hole. It should fit perfectly! Hold it a couple of seconds to let it stick. Now, get your can of fruit, beans, whatever and tie the string around the can. Let the can dangle, it will pull the paint stick to the ceiling and secure the patch to the ceiling and stick. This way, your patch won't push back inside if you push on it. Let this sit over night. When it seems secure and dry, (push it a bit) then you can cut the string close to the patch and maybe sand the knot off if it is sticking out. Put the can back where it came from. Spackle the edges of your patched area, feathering the spackle out and let it dry. Wipe with a damp cloth, or sand, your choice, and put another thin coat of spackle all over the patch and edges, feathering the edges, and let dry then sand or wipe. Paint to match and there, you're all done! :) It's not as daunting as it seems. You can do this, I have faith in you. Heck, if I can do it, anyone can!:) Good luck