Very easy child's sweater by Margaret Hubert

This pattern is on Amy’s website. I’m stuck on the row that reads knit all sts to neck opening, then cast on 4 sts, join as one piece again and continue knitting on other side. When I cast on the 4 sts which thread am I suppose to use. The thread is not on the center. Its on the other end.

Switch the needles in your hand so that the working yarn will be on your left. CO the 4 sts and then turn your needles around again to continue knitting the other sts.

What I’m seeing in the pattern is that you knit across, then cast on four. Use the same yarn you knit across with. Backward loop is good for this kind of cast on. Then, with the same yarn, continue across the other side. Any extra yarn that you added to work the two sides separately can be cut and woven in.