there are some good tutorials to watch to show you how-
you fold your bias strip in half lengthwise, press, line up the raw edges to the raw edge of your runner top, leaving a tail (to join as you come around) stitch your bias binding to the front of your project using a 1/4" seam--when you come around to the beginning you (overlap) the two ends; cut to the size of the binding (often 2 1/2") put the two ends right sides together and join with a diagonal seam, press and continue to stitch binding to the top. press to set the stitches then fold to the back and hand stitch into place covering the seam line. the mitered corners? when you are coming to the corner put a (dot) exactly at the *turn-point* (if using a 1/4" seam then the dot would be 1/4" from the corner- 1/2" the dot is 1/2" from corner)
stop exactly on the dot. remove the quilt, fold the binding straight up, then straight down-lining up the next edge and continue at the 1/4" (or mark you are using) and continue to the next corner.