How do I make my Auto Attendant be the main greeting?

Hello!

I've set up our auto attendant and I would like to make it our main greeting, can I do this somehow? Or am I just missing the complete point of it? I'm just not sure how a customer gets to that. I think I might need to figure out how to re-record our greeting and mention the customer should dial this extension so that they can get to the attendant? That doesn't sound right....

Please help and thank you!!!