NOTE: If you do not have access to a Windows Phone device, you will need to use hardware virtualization to emulate a Windows Phone device. This is taken care of by the Hyper-V server-based virtual machine, and it will be used to emulate the different Windows Phone standards. However this technology comes at a price in that you need to have a machine capable of running it. What this means is that you need a multi-core, 64 bit processor and that your system BIOS has second level address translation (SLAT). You can get a further explanation of these requisites here: How To Get Windows 8.
Once you have all the above installed correctly, you can now start up GameMaker:Studio. The first thing to do before starting to test or create a Windows Phone game, is to set up the Preferences for the Windows Phone module. You can get to the Preferences from the File drop down menu, and then you should select the Windows Phone Tab which will look like this:
There is not a lot to this section, and all you have to do is check that SDK Status says "OK". GameMaker:Studio should have already performed the necessary checks when you upgraded to the Windows Phone target module, but if not and the status does not say “OK”, you can click the Check SDK button to force GameMaker:Studio to perform this action.
You can also select the device that you wish to have GameMaker:Studio use for testing your game on. The available options are:
Device - Your own Windows Phone test device, plugged into your PC by data cable.
WVGA (512mb) - Emulates a memory-constrained Windows Phone 8 phone with a display size of 480 x 800.
WVGA - Normal Windows Phone with a display of 480 x 800.
WXGA - Large Windows Phone display at 768 x 1280.
720p - HD display at 720 x 1280.
Note that you can change the emulator target at any time through the preferences, and should you have any problems with the emulator, as long as the SDK is installed and checked, you can always test using a Windows Phone device connected to the PC.
WARNING!When you come to submitting your game to the Windows Store, the final build MUST be made with this set to '''Device''' otherwise your game will be rejected.''