Applying a popcorn ceiling texture also known as acoustic texture is a great way to cover up imperfections in the drywall, add acoustic insulation to a room and hide stained dirty ceilings. The first thing your going to want to do is prep the room you are adding the texture to. Start by taking out all the furniture and putting down drop cloths along the entire floor. Next your going to want to cover the top edge of the wall with painters tape and masking paper. Apply the tape and paper to the top edge of every wall where the wall and ceiling meet, do this along the entire room. Once all the prepping is done the next step is to prime the ceiling with drywall primer, you are going to want to use a medium nap roller on a regular paint roller to do this. The drywall primer acts almost as glue for the popcorn ceiling texture adding an extra level of adhesion. Next your going to want to open your textured paint cans and stir it around with a wooden paint stirrer. I recommend using Behr premium plus textured paint, keep in mind that a 2 gallon can of textured paint covers approximately 100-150 square feet depending on how thick you roll the paint on. Next pour a good amount of paint into a deep rolling tray and immerse your textured paint roller in the paint making sure that the entire roller is covered in paint. Once those steps are completed it is time to apply the texture to the ceiling. Start by working in 4 ft by 4 ft sections, rolling in only one direction and overlapping each pass by about 1 inch. When working along the wall get the roller as close to the wall as you can remember you have the painters tape and masking paper along the wall preventing the texture from getting onto the wall. Once you finish one section move onto the next and continue this process until the entire ceiling is covered. Let the textured paint dry for at least 6 hours, once it is dried you can then apply a coat of ceiling paint over the dried textured paint using a medium nap roller on a regular paint roller to finish up the job.