In case of iOS devices, you can find the settings at iPhone settings>Mail, Contacts, Calendars.
In case of Android, it depends on makers so cannot be specified but almost case there is a settings area for Mail, Contacts, Calendars.
If you set up the calendar account, Awesome calendar will sync them automatically.
In case of iCloud calendar, it is not possible to add your Apple ID to the Android settings, in this case you need to link your iCloud calendar with Google account so that your system calendar is able to sync iCloud calendar via Google.
If you do not know how to link your iCloud calendar with others, please refer next link.
iCloud: Share a calendar with others - Apple