You're going to increase 3sts on the next row which is a knit row. When you've finished the row, you'll have 45sts total. So you must have 42sts on the needle before the row. Increase about every 10or 11 sts and you should be fine. "Increase evenly" is not a very exact direction so you just want to distibute the increases rather than bunch them all in one place. There are videos under the Free Videos tab, Increases if you'd like to see different kinds of increases.