How do change version of my game from version 4.3 to 4.4?

When you downloaded 4.4 Version of UE, you can click on “Launch”.

http://puu.sh/aW5KF/2f657edc65.png

If you did this, Editor will start up and show a window where you can pick a project. If you now pick a project that isn’t updated for 4.4, editor will tell you to upgrade it.

You have to choose between overriding your project or creating a copy.
I would always create copy, because upgrading a project from one version to another can cause problens and you don’t want to destroy you project with this, do you? (: