Place your first piece of drywall at the corner of the stud wall. If there are no obstructions, nail the drywall to the studs at 8-inch intervals, using drywall nails.
Measure the distance of any obstructions or openings on the wall from the corner where you're applying the first drywall panel. Mark these measurements on the drywall panel with a pencil and straight edge. Cut along the markings with a utility knife and snap off the excess pieces of drywall. Nail the drywall to the studs after you've completed this step.
Place drywall tape over the seams between pieces of installed drywall. Cover the tape with joint compound, applied with a taping knife. Spread the compound as smoothly as possible.
Sand the compound smooth with sandpaper after it has dried. Wear a filter mask to avoid inhaling the dust you produce, and vacuum the excess dust frequently with a shop vacuum.
Place a furring strip vertically onto the wall at the corner of the room. Drill holes at 8-inch intervals through the furring strip and into the foam and concrete wall behind it. Insert a masonry screw and tighten it until it's flush with the furring strip.
Place your next furring strip 16 inches from the first strip, measuring from the centers of the strips. Continue across the wall. Place the last strip at the corner of the wall, even if it isn't less than 16 inches from the previous strip.
Apply drywall panels to the furring strips, using the method described in the first section.