Slip-stitch rib (multiple of 2)

Hi, I am working out of a knitting book by Marilyn Saitz Cohen.
I am making a sweater and have completed the front and back. I am having great difficulty with the sleeves. I am to Cast on 24 sts work in pattern, (which is the Slip-stitch rib) increasing 1 st. each side every 5th row to 20 inches. When I add on I get off the pattern. I do not know what I am doing wrong. How do I keep the pattern going while increasing my stitches. I have never worked in this pattern before. Hope someone can help. Thanks in advance.

After you’ve made an increase, don’t start the next row the same as the rows that haven’t increased. Knit the increased sts in stockinette, then start the st pattern. After you have more sts you’ll be able to incorporate them into the st pattern

I also needed help with this, thanks for asking - and for the answer. I muddled through my last sweater (and will now undo to fix the sleeves!). My other sweaters didn’t have pattern on the sleeves, so it wasn’t an issue…