There are several ways to cast on your knitting .I prefer this method, only because I was thaught this as a small child.
leave a length of yarn approximately 1”, for every stitch to be cast on, place the long end of your yarn over your left thumb, and the strand from the skein over your index finger. Close your other fingers over the strands to hold them against your palm
Place the needle in front of the strand around your thumb and bring it underneath this strand. Carry the needle under and over the strand on your index finger.
Draw through loop on thumb. repeat until you have reached the required number of stitches.