Hello there,
I have the same machine and this is how I set it up for FMQ. It works very well - but you are right there is nothing in the manual about it.
You will need the "Convertible Free Motion Quilting Foot Set for 1600P" Part No 767-433-004 (this contains a foot holder, open -toe foot and darning plate). If you also buy the "Free Motion Frame Quilting Feet Set for 1600P" Part No 767-434-005, you get another open toe quilting foot and an excellent ruler foot. The second set requires the foot holder and the darning plate from the first set to function.
1/ Attach the open toed free-motion quilting foot (or ruler foot).
2/ Unscrew the standard needle plate and attach the darning plate for free-motion quilting (this covers the feed dogs)
3/ Set stitch length to zero.
4/ Set pressure foot pressure to zero.
5/ Lower the upper tension a bit.
6/ Adjust free-motion foot height as desired.
I hope this is of some help. I'm sure you will love it once you get going.
Best wishes.