Measure the height of the wall with a tape measure. Transfer the measurement to the zip bead and cut the zip bead to size with tin snips. Take caution not to bend the zip bead when cutting it.
Place a liberal amount of drywall plaster onto a drywall putty knife and then coat both sides of the corner with a skin coat of the plaster. Apply the coat the full length of the corner.
Place the zip bead against the corner. Start at the top of the bead, press the drywall knife against the bead and run the knife the full length downward to press the bead into the plaster. Repeat the process on the other side of the corner.
Apply a coat of plaster over the zip bead with the drywall knife. Extend the coat of plaster onto the wall beyond the beard by an inch or two. This will allow you to feather the plaster once it dries. Allow 24 to 48 hours' drying time. You will know the plaster is dry when it turns white and no longer looks grey.
Sand the surface of the plaster with a sanding block to feather the seam between the plaster and the wall. When finished, both sides of the corner will blend into the drywall.