How do I choose what type of increase

I am knitting a short-sleeved baby cardigan. The sleeve is part of the body of the cardie and not knit separately. The pattern is knit in a moss stitch. I am knitting the back and at the point where I am asked to shape the sleeves i.e. Patt to end, cast on 6 stitches. What kind of increase would you suggest I use and do I do it in the knit 1, purl 1 pattern? I am to repeat this for the next row.

Thanks for your help.

The CO 6 sts isn’t the same as a simple 1 stitch increase. Cast on at the beginning of the row using the knit or cable CO. Then work the new sts in the moss stitch pattern along with the old sts. Do the same on the next row…

Thank you for your help. I very much appreciate it as I am sure your suggestion will make my project look less amateurish.