Before you start to crochet you need to make a slip knot.
To make a slip knot you first need to make a loop using the tail end of yarn.
Place the yarn end attached to the ball of yarn under the loop you have just made.
Using your hook pull the strand of yarn you have just placed under the loop through the loop
Keep pulling until the slip knot pulls tight. If the loop is too large pull on the ball end of the yarn to tighten it to the size of the hook.
You have now made your first slip knot.