Research the different materials of egg crate wall coverings made for acoustic use; most come in a foam similar to a mattress pad. (Note that actual egg crate cartons do not provide adequate soundproofing and should not be used).
Measure the area of the room you will be covering. Cut the egg crate material with the razor knife to fit your walls.
Put down the drop cloth and secure it with tape if necessary.
Gather your materials and open the adhesive glue. Refer to the instructions on the glue, then apply evenly to a section of the wall with the Spackle blade. Pick up the egg crate material and push firmly against the wall for about five seconds or until it sticks. Be careful not to drip the glue or get it where you do not intend for it to be as it will not come off once applied. If you do make a mistake, you will have to let the product dry, scrape it off with a knife and start over.
Continue to glue your egg crate wall covering in sections until your surface is covered.
Let it dry for approximately six hours or as indicated by the adhesive glue manufacturer's instructions.