Hi, I am a very new knitter and this is my first project besides something square. It is a toddlers sweater and the sleeves are set into the shoulders. My problem is how to sew them in. I knit the front , then the back and then I had to join up the shoulder seams now I have to sew in the sleeves but the stitches are not going the same way. I’m confused as to what stitch to use to knit it up. Help me please.
Debbie
Seaming sleeves can be a bear, particularly at first!
Read this article and see if it helps!
for the few sweaters I have made I turn the work inside out and sew the sleeves up that way. 
now I have only been knitting 9 months so I don’t knot if this a good way or not, but it works for me!!
Hope this helps.
I still use mattress stitch, but I pick up a stitch from the shoulder and one from the sleeve. First, though, I attach the sleeve to the armhole by tying short pieces of yarn to the top, bottom and sides. Then I start seaming at the top, so if there’s any adjustment needed, it’s in the armpit.