Hi and welcome to the forum!
Keep repeating rows 1 and 2 until you have 4 inches. End by doing a row 2 rib and increase one st on this row. So the final row 2 would become P1, Kfb making a total of 3 sts. Turn the work and follow the next direction. A kfb is a knit front and back and you can see a video for that here
. Or you could do your favorite increase in its place.