Clean the leather covering on your couch with liquid facial soup formulated for use on mild skin. Dampen a clean cloth with water and place a spot of soap in the cloth's center. Work the soap on the cloth to a lather and then wipe the surface of the couch with it, removing any dirt. Take care not to wet the material beneath the leather through the tear. Dampen a second cloth and rinse the soapy residue off. Pat the couch with a dry cloth to remove any moisture.
Trim any ragged edges from the torn leather if present. Use a sharp pair of scissors to cut frayed edges from the torn sides, or any edges that curl sharply at the tear. You'll need sharp level edges at the tear to use the repair backing contained in the leather repair kit.
Find a leather kit with colorant that matches the color of your couch. Cut a piece of the canvas backing material so that it's slightly larger than the torn area. Lift one of the edges along the tear in the leather and slide a piece of the canvas material beneath the tear. Slip the material under the leather covering so that all edges of the tear rest on the canvas.
Spread the adhesive contained in the repair kit along the bottom of the torn edges, covering the area of the leather that rests on the canvas. Use the palette knife to spread the adhesive beneath the leather. Press the torn pieces flat against the canvas. Hold them in place for 30 seconds to 1 minute, until the glue begins to set. Wipe the palette knife clean of the adhesive with the dampened cloth.
Spread the leather filler contained in the repair kit into the area between the torn edges. Use the filler in any area on the canvas not covered with the torn leather, building the areas up to the same height as the surrounding leather. Spread the filler with the palette knife. Allow each layer of filler time to dry before placing the next. Drying time will vary according to local conditions, but the repair kit manufacturer suggests general drying times.
Place an additional layer of filler over the edges of the leather as well as the filler area once you've reached the height of the leather. This last layer creates a continuous patch over the torn area, concealing the torn edges of the leather. Allow the last layer to dry according to the manufacturer's suggested drying times.
Sand the last layer of filler with a fine-grit sandpaper, feathering the edges of the filler against the leather of the couch to smooth further the line between filler and original leather.
Use a clean cloth to wipe away any residue left from sanding the filler.
Place a small amount of colorant onto a clean cloth and rub it into the filler. Continue to add colorant until you have a depth of color the same as the color of the leather of your couch. Allow the colorant to dry for two hours.
Coat the repair patch with leather sealant, rubbing the sealant in with a clean cloth. Wait 24 hours for the sealant to dry completely before using the couch.