Picking up stitches for thumb gusset
"Now you'll knit the thumb. Join yarn, then knit the 15 held stitches as p1, k1 tbl rib. Pick up 7 stitches along the thumb gusset and continue p1, k1 tbl. Knit this rib for 7 rounds, then cast off."
Am I correct in interpreting this to mean that I should knit the 15 rib stitches once all the way around; then again, increasing by picking up 7 stitches on the outer part of the thumb; then knit 7 more rounds?
Also, to pick up those 7 stitches, should I just pull them through between regular stitches or is there some other way to do this? I tried looking for videos, but I couldn't find anything that really applied to a project like this.
Thanks in advance!