Sleeve gap on top down

Hello I am knitting a top down sweater there were no added stitches to form all eve just placed stitches to waste as directed.
I am trying to close gap when I start sleeves I can not find instructions for this only for sleeves that extra cast on stitches were added
Is it done different? Do I still pick up stitches and then what??

What is the name of your pattern?
Are you knitting the sleeves in the round? If so, when you start to knit the sleeve pick up a couple of extra sts from the body on either side of what would be the side seam. On the next row, you can decrease the extra sts with k2tog and ssk.

If you cast on some number of sts at the start of the body of the sweater, the extra picked up would be on either end of those picked up sts.

In either case, even if you don’t pick up the extra sts, you can use the tail of the yarn used to knit the sleeve to close the small hole on either side.

Thanks for reply the pattern is Venlig Pullover.
Do u have a video suggestion for stitch pickup

Yes I am knotting in the round
You can use this method

or you can simply pick up an extra stitch on the body side of underarm and decrease it on the next round. The video method does seem like a neat way to close the gap between body and sleeve.