Measure the length, width and depth of one of the loveseat cushions. This helps determine how much fabric is needed per cushion.
Browse through a nearby arts and crafts store for fabrics. The fabric should be sturdy but thin, free falling, lint free and have little elasticity. Purchase a heavy-duty needle to fit the sewing machine if you do not already have one. Buy extra fabric for the seams and piping for the top and bottom edges.
Purchase memory foam or cushion material to make new cushions in case old cushion fillings are unusable. A nearby fabric store can cut the cushions down to size and even provide direction to finding the right cushion material based on your loveseat and preferences.
Use a seam ripper to take the previous cushion cover apart. Use these patterns to trace the outline on the new fabric. Lay the patterns on the backside of the fabric, then trace and cut the new fabric to fit the cushion. Allow a 1/2 inch of extra fabric all the way around each piece.
Mark a 1/2-inch line all around the edging of the fabric pieces. Stitch the piping on the right side of the fabric at the 1/2-inch mark. Place the right sides together, and using a straight stitch, begin to sew. Leave the bottom edge open to allow the cushions to slide in.
Slide the cushion in, making sure each corner is snug. Line sewing lines up accordingly.
Sew the zipper onto the remaining open end of the cushion. Follow package instructions accordingly when installing zipper closures. Cushions may also be stitched closed if you prefer.