Get a 10.5/6.50mm crochet hook, or any similar crochet hook you happen to have, and some yarn, medium. I don't suggest really fuzzy yarn, it will lead to many knots and frustration, especially with beginners.
We'll assign each finger a number for our purposes. Hold the end of the yarn between 1 and 3, left hand, with the yarn looped around 2 as shown
Next, stick the crochet hook between 1 and 2 as shown, under the yarn, over your hand.
Twist the crochet hook in the yarn twice, as shown in the video and picture. There should be a loop around the hook, and the two strands of yarn twisted together on the side.
Loop the yarn around the hook a second time, as shown. This should actually be hooked...well, on the hook.
Now , yarn under hook, pull through the first loop, and you've begun your chain of yarn.
Repeat steps three, four and five over and over again, and you'll end up with a chain of yarn.
Practice makes perfect, so focus on keeping the loops all the same size.