I am going to show how I cast on for a knitted top down hat. This has a lot of pictures to show the method. I use the Magic ring Method usually used in Crochet.

 The picture below shows that I tied the string that was hanging with the working yarn to secure the circle. I usually just knot the end in so I don't have to weave it in later.

 This picture below shows after I have knitted a few rows and did some increases.

 The picture below shows a hat well on its way!!

 God Bless You All!!