Measure each wall you'll be installing crown molding on, using a tape measure, and round your measurements up to the next foot. This will let you know how much crown molding you need. If there are only a few inches to the next foot, round up to the next size up so that you have enough to work with.
Draw up a simple blueprint to determine how you will lay out your crown molding on your walls, using paper and a pencil. Number your walls on your blueprint so that you don't get confused.
Hold a scrap piece of crown molding up against your walls in the spots you'll be installing the molding. Mark the wall with a pencil at the bottom of the molding to ensure proper placement. Find the studs on the walls with your stud finder and mark the places on your wall where the studs are with your pencil as well. Make sure these marks are below where you'll install the crown molding so that they're not covered.
Measure the angles of the corners of your wall with your framing square or 360-degree adjustable protractor. Just stick your tool in the corner and write down the angles. Account for any corners, whether they are positioned inward of the wall, or sticking outward of the wall.
Mark your crown molding with a pencil to the correct lengths, and then mark the angle they'll be cut at with a pencil. Remember that you must know the order in which you'll install the crown molding so that pieces fit together like a puzzle on your wall.
Cut your crown molding with your miter saw, setting the saw to the same degree as the board needs to be cut at. Use your markings on the crown molding as guides. Before installing the on your walls, make sure the crown moldings line up correctly with one another and form a corner.
Align your cut crown molding pieces on the walls, using the pencil markings on the wall to help make sure your crown molding is on straight. Nail the crown molding into the wall, using the 8d finish nails and your nail gun, nailing into the studs in 1/2 inch below and above the top and bottom of your crown molding. Add the acrylic caulk to the corners if there are gaps, wiping off the excess caulking material and letting it dry.
Prime and paint your crown molding with a paintbrush once the molding has been installed. Make sure all coats are dry before painting the next coat of either primer or paint, and also use painter's tape to tape both above and below your molding to ensure crisp, clean lines.