It changes the color.:rofling: Sorry!
Just knit the first rounds as the pattern says, then when you get to the ribbing, you won't have to worry about securing that color by knitting it with the tail.
Just knit your first stitch, purl with the other color, knit, purl with the strand and the tail together, k, p, k, p. . .
Just make sure you bring the yarn to the back after the purl before you do the knit.