I think you are looking for the options in the setup menu before you go to your load data for the atmosphere options.
Sean has the main link here:
Shooter - Ballistics Calculator for iOS and Android
The Op Manual here:
Operation Manual for Shooter
I usually use the auto update feature from my GPS or I look it up before in the field and load it ahead of time. I verify it in the field with my watch and/or a Garmin unit.
As for the GPS app when you go into your phones settings you should be able to turn on stand alone GPS, Google, or your carriers. I turn them all on, but Shooter will be looking for the data from the standalone GPS. "How do I know this?" if it is off the app won't update with current info.