THE PIC IS ABOVE THE INSTRUCTIONS.............................
First you would start stitching your binding on leaving at least 8-10" of the end not sewn down, Also when you near where the binding started you would stop stitching , about 10-12" from the start. Leaving a gap in the binding, so you have enough space for the joining part.
Next you would bring either end of the binding and lay it as shown. These next two steps here allow you to get the exact size for joining.
Now bring to other side OVER the top of the first side and flip up the same way as the first side. If you click the pic you will get a close up view.
This is how you determine where to cut. Cut those two little doggy ears off directly across the top of the binding strip. As shown.
Now open the ends up and place them right sides together, make sure not to twist them the wrong way. Put your pins in as shown and check to make sure they are not twisted the wrong way. Now stitch on the diagonal. Just like you would if joining strips to make the binding. You can draw a line or just aim and shoot.
Now before cutting those little corners off, it is a good idea to check and make sure it is not twisted and the fit is good. I've never had the fit to be wrong, but I have on occasion twisted in the pinning process.
This is how your binding will look when finished and will lay completely flat, and is ready to stitch to the quilt.