This is How to Configure your screen to use Air Display
Open up system preferences but clicking on the Apple Menu in the top left hand corner and selecting system prefrences

Select the Displays icon under Hardware

Click on the Arrangement tab.

When in this window you have a couple of different options.
1. You can select to mirror the Displays
This will allow you to see everything the computer sees
You can control the computer from your idevice.
This is not the setting most people use because when using an iPhone or iPod it can be hard to see and control the whole computer screen.
2. You can choose to use your iDevice as an extra screen.
When using it as an extra screen you can determine what you want to see on your screen
In an instance like this (Pic Above) You can choose to drag over just a code window to your iDevice screen.
You will drag the code window over to the right off the computer screen and you will see if show up on the iDevice screen.
If you have any questions or issues feel free to contact our Support Manager Ben Myers