Canvas Size issue

Hi, I’m very new to Unity and the main menu is the very first thing I am attempting. Bellow I posted 2 pictures, my issue is that the canvas size doesn’t represent the size of the game screen so I can’t place my buttons further out, as soon as they cross the canvas they disappear when I run the game. What can I do about this?

The first thing I would look at is where your anchors are. Is this a game for mobile, Standalone? Those things help when trying to give advice.

Look up CanvasScaler
http://docs.unity3d.com/Manual/script-CanvasScaler.html

Also:
http://docs.unity3d.com/Manual/HOWTO-UIFitContentSize.html