Clarify patter instructions

I’m working a boy cardigan sweater. Body is worked in one piece sideways. I’ve done this much:
BACK: K68 (76-91-100) for Boy’s Version or K85 (109-123-137) for Girl’s Version. Turn. Leave rem 68 (76-91-100) sts for Boy’s Version or 85 (109-123-137) sts for Girl’s Version on st holder. Place second set of markers at each end of needle. Proceed in garter st until work from second set of markers measures 6 (6-6½-6½) ins 16.5-16.5) cm], ending with RS facing for next row. Leave sts on spare needle.

I’m confused on how to do:
LEFT FRONT: With RS of work facing rejoin yarn to sts on st holder.
Neck shaping: Next row: K2tog. Knit to end of row. Next row: Knit to last 2 sts. K2tog. Rep last 2 rows 6 times more.
Boy’s Version only: 54 (62-77-86) sts

When the pattern read Turn, I just did a short set of 91 sts to measure 61/2 inches. How to join the yarn? Any help would be greatly appreciated.

To join yarn just start knitting with a new skein. Can you tell us the name of the pattern please and provide a link if possible?

Here’s the link to the pattern.

Just join new yarn and continue then?

Yes, just start a new skein and continue. This is a common technique when you have to leave some stitches on a holder or waste yarn for sleeves or yoke. Your pattern doesn’t say to cut the yarn so starting with a new skein is probably easiest.

Thank you. I was totally second guessing myself.