Having trouble with pocket on front of sweater

[AKchick]

Hi everyone, it's been a while since I have been on here. Once school started things have just been constantly happening. Afterschool activities and the chores and errands I need to finish during the day have taken over. Lately though I have been finding time to work on some of my Christmas knitting but am having a hard time understanding the directions on one of my projects at the moment.

I am working on the Lion brand wool-ease thick & quick fast & easy sweatshirts (it is from a booklet of patterns of theirs I purchased). I started the front and the directions are trying to tell me how to start a pocket, but I have never done that before so I don't know if it is looking like what it is supposed to look like. I will give you the directions and tell you where my trouble lies.

Work ribbing and 3 rows St st as for back ending with a WS row. Adding Pocket placement to front Work first 7 sts of front; place next 40 on a holder; keeping holder to RS of work, cast onto the right needle the same number of stitches until piece measures 12 1/2" from beg, ending with a WS row.

My question is, when I put the 40 sts on a holder, do I cast on with a new skein of yarn? Then, how do I work those to the end and is there supposed to be a big gap between the newly cast on yarn and the sts on the holder?

My brain just isn't computing this, so thanks for any and all help!