Remove the seat from the chair. This usually requires simply turning the chair upside down and removing the screws that are holding the cushion in place. Remember to reserve the screws so the cushion can be reattached after the cushion is covered.
Pull away any existing fabric from the dining room chair cushion. If the fabric is stapled in place, use a flat-head screwdriver to pry the staples away from the underside of the cushion. If possible, keep the original fabric intact to use as a pattern for the new fabric.
Repair the cushion as needed. If the foam is torn, fill the holes with pieces of upholstery foam and glue in place. If you prefer, you can replace the upholstery foam entirely by attaching a new sheet to the base of the cushion with spray adhesive.
Create a pattern for your new upholstery fabric. If you were able to reserve the original cushion fabric, simply trace this piece onto your new fabric. You can also create a pattern by draping a piece of muslin cloth over the cushion and tracing out the shape you need. Be sure to leave extra material on all sides for pull.
Position your seat cushion over the new fabric, print side down. Pull the fabric over to the underside of the cushion and staple in place. Pull the fabric as tight as possible to avoid bubbling and create a clean, professional look. Cut off excess material or cover with a sheet of interfacing.
Attach the seat cushion to the chair with your reserved screws.