Unscrew an embroidery hoop, and remove the inner ring.
Slide two pocket curtain panels onto the hoop. Turn the hoop as you feed it into the top pocket. Fasten the hoop closed, and space the bunched fabric out a bit.
Tie four pieces of twine or fishing line to opposite corners of the hoop. Fasten them together in the center, making the string as long as desired. Tie a scrap piece of twine into a loop around the top knot.
Hang a large ceiling hook from the porch or patio ceiling, if that's where your hammock is located. Place the hook where you'd like to hang the canopy, centered along the hammock's length or over the area where your head would rest.
Hang the hammock cover from the installed hook. Adjust string length with scissors, by tying another knot, or by shifting their positions on the hoop frame so the canopy hangs straight.
Spread out the curtain fabric around the canopy, or tie each side back to the hammock's support posts, depending on the look you want.