Sync all iMessages with computer, iPhone and iPad

Question

I just installed iMessage BETA on my Mac  OSX 10.7.4    How can I change the setting so that when I send from either my Mac, iPhone or iPad they all SYNC from the same place.  I send iMessages to friends and they say that they are getting them from 3 different place, 2 of my emails or my phone.  If I send from my computer their replies only come to my computer.  I would like to send 1 message (either from computer, iPhone or iPad) and have it come form ONE address and be on ALL my devices and when a person responds have it be on ALL devices.
Please instruct.

Answer 1

On your mac log into Messages with the Apple id/email address you're using. Make sure in preferences that this is the account that's enabled and appears as the "address you can be reached at".
On your phone in Settings at Messages make sure iMessage is 'on". At "Receive At" enter and make sure the same Apple id/email address that you used on your mac is entered. You should then see below the Apple id "you can be reached for messages at " your phone number ( entered automatically ) and your email address. Below this is Caller id you will see your phone number and email address here. I have my phone number checked because not everyone I text will have my email address and thus would not recognize that it's from me. All my messages sync between my ipad, mac, and phone so I've left it this way with no issues.
On your ipad in Settings at Messages make sure that the "receive at" field shows your Apple id/email address that you've used and that it shows both in the Apple ID field and below at the "you can be reached for messages at" field.
On my mac, since I have two email, Apple id accounts I have to make sure that the correct one is selected for the Messages account. Initially the wrong one was checked causing a few problems. As long as you're using the same email address on each device and your phone shows you can be reached at two addresses - phone number and email you should be good to go.