Casting on at the end of a knitted row

How do I cast on extra stitches at the end of a knitted row? The directions call for casting on 18 stitches but the only way I know how to cast on is the “long-tail” method.

Look in the Cast on videos for knit or cable cast ons. You would use the first st instead of a slipknot and just knit into it, leave the original st on the L needle and put the new st on it too.