Measure from one end of the sloped wall to the other end. If the wall is shorter than 8 feet long, you will need to cut a piece of drywall to fit.
Transfer the measurement from Step 1 to a piece of drywall, once near the top edge and once near the bottom edge. Connect the two lines with a 4-foot level. Trace down the level with a utility knife to score the drywall's surface.
Stand the drywall on edge with the paper backing facing you. Hold the drywall's top edge, with one hand on either side of the line you scored. Use your knee to lightly tap the drywall, breaking it along the score line. Cut through the paper backing holding the two pieces together.
Flip down the lift's support arms so the two hooks are on the bottom edges. Load the drywall onto the support arms so the paper backing faces toward you and the bottom edge rests on the hooks. Tilt the support arms up so the drywall sits horizontally. Wheel the lift over to the sloped wall.
Tilt the support arms toward the sloped wall until the drywall rests against the wall studs. Raise or lower the drywall along the wall by turning the lift's wheel. Once you have the drywall in position against the wall, drive drywall screws through the drywall and into each wall stud it covers. Use four screws, evenly spaced, for each stud.
Turn the lift's wheel to lower the support arms away from the drywall. Wheel the lift away from the sloped wall. Take a new measurement from the wall and transfer it to a second piece of drywall. Cut and install the drywall against the sloped wall, using the lift. Continue until you have covered the entire sloped wall with drywall.