How to sew in sleeves

I’m ready to sew in sleeves on a baby cardigan (Mr. Bumble from Knitter’s Winter 2004 - stockinette stitch). The body is knit all the way to the arm hole. Should I do this right sides together? Mattress stitch? Directions had me bind off the edge of the sleeves but the armholes are shaped and shoulder seams are joined with 3 needle bind off. I’m confused. Is it a good idea to pin this together the way I would with a sewn piece? I really just don’t know where to go with this.

Thanks for any suggestions or links.


p.s. I’ve never seamed in anything 3-D before on knitting.

I usually use pieces of yarn to tie the sleeve in place. I use mattress stitch, picking up one stitch on each side and working back and forth. Start at the top and work down each side, so if you’re off a bit it will be hidden in the armpit.

So it doesn’t need to be right sides together?

Can I just continue on down the sleeve seam once I get the second side done?

You need right sides together for the three needle bind off, but for the mattress you work with the right side facing you–not on the inside.

thanks Ingrid.