Use the 'stab' method of quilting for this. First stab the needle straight down through the quilt, and pull your choice of tying strand through ( NOT yarn!!!) Then turn the needle and stab the needle back to the top, coming up a short distance from where you stabbed down. Leave long ends for tying. To do this properly, you need to keep your dominant hand below the quilt and your non dominant hand at the top of the quilt as it is easier to control your dominant hand when you cannot actually see what you're doing! You really should have a large hoop or a frame to hold the quilt taut, but I'll bet if you're careful you can do it without!