Help! I'm stuck

I’m currently knitting my first major project, a cardigan for my baby, with a hood. I have knitted the front panels, the back panel and the sleeves and the pattern says to leave 11 stitches at the top of the sleeves, and 17 at the top of the back panel on a stitch holder. Then to join the sleeves (with raglan edge) to the front and back panels, which I have done.
Then it says, using 3.25mm needles cast on ten sts, with rs facing, using same needles and yarn work across 11 sts left on a stitch holder at top of right sleeve.
I can’t fathom how on earth to work with these stitches that are on the stitch holder. I have cast on ten sts, which are on my left needle. If I then knit into the first stitch on the stitch holder, I am going to transfer it across to the right needle, leaving the ten I cast on on the left needle. If I switch the 10 stitches I cast on onto the right needle, the yarn will be on the wrong needle!
I’m so confused! :hair:
Do I need to thread all the sts on the stitch holder onto my 3.25mm needle first?
Would be so grateful for any advice, I hope this made sense!

You have the cast on sts on the needle with the working yarn dangling at the tip of the needle. Transfer the needle to your right hand and using the stitch holder as the left hand needle, work across the 11sts that are the right sleeve.

Thank you so much! That makes sense! :woot:
Will go and try it now.