There is a lot more to these stances than it looks, but I hope I can give you a basic understanding of the basic stances.
below is how you stand at attention. You should be perfectly still.
Step 1: Front Stance (zenkutsu Dachi)
Start with your feet shoulder with apart. then bend your front knee and push your back leg back (duh)
(picture 1, and 2)
For a left front stance, push your right leg back and keep your front leg bent and stationary.
For a right front stance, push you left leg back and keep your front leg bent and stationary.
Always bend your front knee until you can't see your toes. Your back leg should be as straight as you can get it. Your back foot should face forward as much as you can get it.