Open the top cover of the printer.

Place the label roll on the roll holder.

Push the gray plastic piece on the right side firmly against the roll, so the roll sits all the way to the left and can't move.

Pull the label paper forward through the paper path.

Slide the black slider until it presses against the edge of the label paper and holds it in place.

Make sure the label paper lies flat across the roller at the front, as shown in the red box below.

Close the top cover.