How to read this pattern and knitting of shawl collar

I’m up to the shawl collar of cardigan.

the pattern told me to pick up 147 stitches from the right front to left front, which I have done.
but I don’t understand how to continue.
It said,

“Starting with 2nd row (so that ws of body becomes rs of collar), work in 1X1 rib as given for Button Band as follow:
Work 1 row.
Keeping rib correct as now set, now shape
Collar as follows:
1st row. Rib 87 and turn.
2nd row. Sl 1, rib 26 and turn.
3rd row. Sl 1, rib 31 and turn.

so, where do I start?
and what does it mean by “Keeping rib correct as now set, now shape” ?
what do I do after “turn”? read the next row’s instruction? or keep knitting the pattern? where do I follow?

thank you so much if anyone can help=)

Welcome to KnittingHelp!
You have the picked up sts on the needles now. Work a row in 1x1 rib. “Keeping rib correct” means to maintain the 1x1 rib (keep the column of knit and purl sts) on all the following rows.
After the turn, work the instructions for 2nd row. These are short rows. The general idea is shown on the Tin Can Knits website here:

See the photo for shawl collar.
The idea is to put extra rows into the collar, especially at the back.