AwesomeCalendar can’t DIRECTLY add or remove google calendar. Firstly, user should set up calendar settings for this. If user set up google calendar account in iPhone, Awesome Calendar will automatically show google calendar event.
You can add google calendar account at the following path in your device

iPhone/iPad settings>Calendar>Accounts>Add account

If you use google multiple calendar in a single google account, visit below website, and select all calendar to display in Awesome Calendar.

https://calendar.google.com/calendar/syncselect