Remove the tacks or staples holding the current fabric in place with a staple remover. Collect them in a container as you proceed. Remove the fabric and set it aside. Skip this step if you are upholstering a new sofa.
Cut the stitches joining the different parts of the old fabric with a stitch ripper. Alternatively, take the horizontal, width and vertical measurements of the back, inner back, lower front, outer and inner sides and arms of the sofa. Include 2 inches for seam allowances with each measurement before recording the findings. Also measure the sofa cushions' length, width and depth, plus 2 inches.
Spread the upholstery fabric face down on a clean table. Spread the fabric cutouts over it and trace along their edges. Alternatively, transfer and trace the recorded measurements on the fabric using colored chalk. Cut along the outlines using sharp fabric scissors.
Center and lower the new fabric for the sofa's back in place over the frame. Assign a helper to hold the sofa while you begin inserting staples along the bottom back to secure the fabric to the frame. Pulling the fabric taut, stretch it up over the back and insert staples along the upper edge to secure it in place. Tuck the edges along the sides of the fabric into the frame and staple in place.
Spread the fabric for the inner back and seat in place and insert the edges into the frame. Staple the top edge and sides of the fabric to secure it to the sofa padding and frame. Continue securing the fabric to the outer and inner sides of the sofa, and the lower front panel.
Sew fabric for the top and front panels of the arms to the padding in place using a needle and matching thread. Cut excess thread off with scissors.
Sew slip covers for the sofa cushions by hand, or use a machine to reduce time and effort. Attach a zipper to one side so you can remove the cover easily when washing it. Also sew a tassel on each corner, or decorative trim along the sides of the cushions for added effect.