How to make your client larger/full screen, and generally run better.
***Optional (Get Launcher Here)***
Open Bethlehem Launcher and click launch
If you skipped downloading the launcher and downloaded the client directly start here
Once you have the client open. Locate the high performance link at the top of the client and click it.
You will get this popup. You should choose yes. It's asking if it can use your computer's resources as a normal game would.
At this point it will start to open a new client directly on top of the old client. Drag the new client down just a bit so you can close the old.
Now just use the client we still have open. It will allow you to switch screen sizes, even to full screen, and you'll generally see the game run better.
Video of entire process here: