Clear any debris from around the base of the post. As you pull the post out of the ground, debris on the ground could fly up and cause injuries. Wear safety glasses and gloves at all times to protect yourself.
Set the wooden plank on the ground near the post and place the jack on top of it. The wood will help to distribute the downward force produced by the jack and will keep it from sinking into the ground as you pull the post.
Wrap the chain around the post, securing the chain to the post by passing one hook through a link in the chain. Pass the other hook through the hole in the bottom of the moving portion of the farm jack. Make sure the hook is secure in the hole to prevent it from slipping loose as the pole comes out of the ground.
Hold the top of the jack in one hand to steady it, and move the handle up and down slowly to move the jack upwards. The moving portion will climb upwards with each push of the handle and the post should come easily out of the ground.