Ah, well nothing like going back and looking at the pattern with a different mind set. Yes, you should be turned so that you're next sts go on the knit side. You're now going to join at the center back and center front to knit in the round.
"On the last row (I take this to be the current knit row),
stop while there are still 4 sts on the left needle (4 sts from the first side piece).
Slip the 4 sts remaining on the left needle onto a cable needle and hold in back, K4 from left needle (These are the first 4sts of the second side piece.)
K4 from cable needle (this is a C8B and sits in the middle of the back),"
This joining row is done on the knit side, first to form the cable up the back and then again to form the cable up the front. You can see the way the cable crosses at the join in the photo.