Baby cardigan

Please can someone break this part of the pattern down to a easier version for me. I’m so confused

Sounds like joining the sleeves on a bottom up cardigan. You have the sleeves already knit and on holders. The body is on the needles maybe with two sections of bound off sts for the underarms?

Work in the pattern (S1, p1, k1, p1, k1, p17) across one of the fronts, purl across the first sleeve, purl the 41 back sts, purl across the second sleeve and finally finish up across the second front piece.

You can work the sleeve sts from the stitch holders if they are on metal or plastic holders. If they are on scrap yarn, place the sleeves on a spare needle or on your left hand working needle, then purl across them.