Knitting lacy arrow edge border

My directions start by saying (working over 21 stitches) row 1:knit 3,yo,k2tog, etc.

Does this mean cast on 21 stitches to start?
Obviously I,m a novice knitter!

This sounds like the directions for the pattern repeat. See if there are directions for the cast on if you read further down the instructions. Can you give us a link to the pattern or a pattern name?

Patterns almost always specify how many sts to CO to begin.

Thanks everyone. I took it to knitting store and was told that I was to cast on21 stitches.
Again, thank you.

I end up with 1 stitch short after row 2
The pattern is for Fiesta Cottonista Tunic . Got the pattern from Patterfish

Is this the pattern?
It may be that you missed a yarn over in row 1. You can check by going back to the stitches on the needle and checking for the k1, yo, k2tog etc as the directions for row 1 tells you.

That’s the one. I’ll try again and get back to you!