Apple id and password on 3 macs

I am not new to using a mac, but in my working days I had an IT dept to sort out any issues! In my seventieth year I am confused about apple id. I recently purchased an ipad for my wife and I currently have two mini macs. Having set up an apple id on one mac do I need to set it up on the others or does having the same email address on all three automatically set the id on the others. I am trying to get all three apples to communicate with an Apple TV 3rd generation my son gave me recently.
Many thanks Retired-Robin

If all of the Apple devices are used by you, use the same Apple ID to keep things sync'ed and consistent..

The Apple ID username is an e-mail address, but an e-mail address is not your Apple ID, if that makes sense.

What Ashwin is saying is that if you know your Apple ID (which may or may not use your normal email address as the "username"), then just open iTunes, log into the store, and turn on Home Sharing. You're then all set to access the media on those machines from your Apple TV (you may have to input the Apple ID credentials one more time on the Apple TV itself).

Thank you both, by the way Chas when I visited Victoria BC a short while ago I left a really good white coat in a restaurant and did not realise until I was back on the ferry. If you see a guy in a smart white coat tell him I'd like it back please!!!

Will do!

Apple TV

Apple TV all up and running fine thanks...