Pattern direction help

Stuck on a direction:
Keeping armhole edge straight, cont to dec at neck edge on 3 foll 4:) th rows. (17 sts)
It’s my first sweater and want to keep at it!

Welcome to the forum!
If you call the row that you’re on at the start of these directions row 1, then you would dec at the neck edge on rows 5, 9, and 13. No decreases on the armhole side.
Enjoy knitting that first sweater.

Do I decrease at my first row or wait until row 5?
Thanks so much for your help!

Since your directions say, “… [U]cont[/U] to dec at neck edge on 3 foll 4 th rows”, it sounds like you’ve just done a decrease so don’t dec on the first row. The next decrease would be row 5

Bummer, I did a decrease :(. Oh well.
Thanks you though!