The binding is the very last thing you do.
You have to layer the quilt sandwich -- top, batting, backing. Spray basting is the fastest and easiest way to do this, but you can also do it with safety pins or with large basting stitches done by hand. The important thing is to make sure there are no wrinkles, especially in the backing. You typically don't trim the batting until after the quilting is done.
How big is the quilt?
By top-stitching, do you mean decorative stitching on the quilt top? Or do you mean the quilting?