Assume your new reel of tape is on the left spindle.
Tape should be unwinding off the far left side of the
reel, unwinding as the left reel turns counter clockwise.
From the left reel, tape is threaded UNDER the LEFT
tension arm, OVER the LEFT idler, UNDER the tape head-
stack, BETWEEN the capstan and pinch roller, OVER the
RIGHT idler roller, and UNDER the RIGHT tension arm,...
to then be spooled up on the RIGHT side of the takeup
reel, while also spinning the takeup reel in the counter
clockwise motion.
There's no way I can get my diagram to lay out correctly on this bbs post. I emailed you the homemade diagram.
Good luck with the 388, I think it's a great machine, and is a good choice for the hifi/quality minded home recording musician.