If you are talking about T:ANE do this:
Make sure T:ANE is closed first.
Start T:ANE.
At the launcher, click on settings and the General tab will open.
Click on Full Screen checkbox.
Scroll the window on the right to change the resolution that you want.
You can keep this setting to stay full screen all the time, or optionally uncheck this box to give you the option of running windowed, which you can resize or maximize.
Personally I recommend unchecking the full-screen checkbox because if you want to run another application, such as Google Earth, T:ANE won't minimize, and will remain ready to click on again, and if you have two displays, you can keep other applications open such as Google Earth, or a browser and not cause T:ANE to minimize when clicking away from it.
