popup screen

am doing a space shooter game. am creating the GUI main menu in which there are 3 buttons namely startgame, instructions and quit. my question is i want to let the player know what are the controls, so if the instruction button is pressed i want to popup a window showing the controls. previously i was creating separate scene for this, which i came to know was incorrect way. i want to popup a screen when the instruction button is pressed. just tell what is the correct way to display the controls when the control or instruction button is pressed. thanks in advance for the response.

You can do this using GUI or 3D Planes. Create a Instructions Popup in Hierarchy and make it inactive by default… When instructions button is pressed make it active.