How can i get my webview to auto-resize with the size of a window in xcode (Mac App)

Hello, i am developing a Mac app with xCode on my macbook air but i am having one issue i have a web view but i cant get it to resize with a window and currently the web view is activated by a button as i diddnt know the coding to make it automated.

Any help is appreciated.

MacBook Air, OS X Mavericks (