So, start by grabbing your blind stitch foot. My machine came with one, so I'm guessing it's pretty standard. My last one didn't, but it was a handmedown, so...
Anyway, switch out your regular presser foot for the blind stitch foot.
There's a little screw on the presser foot. If you turn this, you adjust the distance of the guide position
You want it to lined up with the fold.
Sew, just catching the fabric fold with your needle
Blind stitch/hem, baby!