Make a button or a "sprite button" visible at the same time you're displaying the "Game over".
On mouse click (or on button clicked) use the system action "Go to layout" and take back to your first layout (probably menu, or something like this).
You can also reset global variables if they need to be reseted and delete the global instances that you may have created along the way.
Also it is a legitimate question and it has already been asked and demonstrated in numerous examples of the how do I FAQ, but you should do a forum search before asking those types of questions and multiplying threads, all your current beginner questions are already answered through the forum.