Hi Angharad,
In AA we get our recovery by believing in a power greater than ourselves. Are you truly the greatest power that there is? If you believe not, then you believe in a power greater than yourself, or a Higher Power. Some people call it God, some people call it Higher Power, some call it HP, some call it something else.
You will hear the term God, "as you understand him". As you are an athiest, then try to put out of your mind what you think God is. This is not a religious program. You can create your own concept.
The vast majority of people entering AA have an issue with the 'God thing'. Whatever you are doing is not working, it's time to change and do something different. Just keep an open mind. No-one is going to make you do anything.
Let us know how you get on with the meeting.