Help with Rowan Major pattern: joining horizontal rows?

I’m knitting Rowan’s “Major” men’s cardigan in its smallest size but I’m a bit stuck with first part of the Left Front piece
(I hope the link goes through https://knitrowan.com/en/free-patterns/major);

“Cast on 6 sts using 10mm (US 15) needles.
Break yarn, leaving these sts on needle.
Onto same needle, cast on a further 5 (6: 7: 8: 9) sts using 10mm
(US 15) needles.
Join sections”

I have finished the 14 stitch pocket piece. Is the pattern asking me to join the 6 stitches with the 5 stitches I’ve newly cast on (I can’t seem to find anything on joining two horizontal cast on rows)? Or is it asking me to perhaps join these two separate cast on stitches with the pocket (even though I have less stitches, I have entertained this theory out of desperation on what to do)?
I’m very confused. Please help?

Welcome to KH!
Thanks so much for the link. The two separate cast on go on either side of the pocket which you have already knit.
Under the Joining section you P1, K2, P2 across the 5 cast on sts, then knit across the 14 pocket sts with the WS of this pocket facing you, and end with P2, K2, P2 across the 6 cast on sts. You’ll end up with the pocket sts in the middle of the cast on sts (25sts total).