If your talking about the black button on top of the tank, then yes, that is how you prime it.. If your fuel lines are not clear, you can remove the line from the carb, and press the primer until you have fuel coming out of the line, then reattach..
If indeed you have a tank with the primer button on top, you might want to look into upgrading to a newer style tank without the primer. It has become commom knowledge that you will more than likely have an airleak through the primer button.