You wrap your yarn from the outside of your thumb down through your index finger. I'm holding the active yarn. That's the yarn coming from my yarn ball with my last two fingers. Then you simply take your right knitting needle, slide it through the loop and slide your thumb out just like this. That is the backwards loop cast on. This is typically used in the middle of projects, such as after you've bound off some stitches for sleeves and you need to increase more. You'll do this in the middle of your work. Anytime that you do the backwards loop cast on, you'll also want to follow it up on the next row with a purl row to lock in those stitches. I also want to show you another way. This is the finger, basically the same motion as with the thumb, but this is how you do it with your finger. You just wrap it around your index finger, slide the needle through and around. Again, that's the backwards loop cast on. When you come to your next row, you want to purl those stitches, row one, or a set up row in most cases as a purl stitch. See how flimsy that is on my needle? A lot of times you'll get big gaps in there because of that. Walking those stitches in with a purl stitch on the next row is very useful to give you a nice, finished edge and to keep your tension in your project. It is a little finicky because if you pull on this side, it tightens that up and you get this bar right here. That is times you'll want to go through and open that stitch up and then purl into it so that you don't mess up your tension and get those big gaps. Again, it's a little more finicky on this side and you want to keep manipulating your stitches on your needles with your fingers to give yourself the grace to knit into those stitches.