you stitch the raw edge of the binding to the raw edge of the quilt- generally on the back for machine binding- then fold to the front & stitch in the ditch (in a perfect world) it comes out very nice & even-
some people fold over to the top then stitch using a decorative stitch along the edge of the binding-
or you can start by attaching to the top, fold over to back & stitch in the ditch from the top- hopefully catching the binding evenly on the back...pin closely (or use glue) to hold the binding in place & stitch slowly...try it out on a small practice quilt sandwich (like pot holders, placemat, something small & easy to work with) to get the hang of it & figure out what works best for you.