Knitting a doggie sweater

I am new at knitting and attempting to do a doggie sweater and need help. The part I'm having trouble with at the moment is the leg openings. Here is what the pattern says: Row1: K5, bind off next 4 sts, K29, bind off next 4 sts, knit across: 30 sts in center section and 5 sts in each outer section. Row2: P2, K3; with second yarn K3, P24; with third yarn K3, purl across. My question is how do I get the second and third yarn in there? This is my first project and I'm lost already lol...Any help would be apprectiated and if someone might know a sight that might have a video that would be even more helpful..thanks!