get input from user and apply force to a rigrdbody

Hi,
I want to know that,
how to get input from an user and use it to add force on a rigidbody .

I mean to say there should be an area to input value on Gui.
Then a submit button.
When it pressed the force should effect on rigidbody.

Thanks for viewing.

See

GUI.TextField - Unity - Scripting API: GUI.TextField and
GUI.Button - Unity - Scripting API: GUI.Button