I have bounced my project in multichannel 5.1 file with logic, and in compressor I encode it in AC3 what really do I need to get a perfect dolby digital certification on my final work?

As I understand it, you need to mix and encode in a studio that has been certified by Dolby. They have stringent quality assurance requirements for everything their logo goes on and your final mix must be done in a facility that has been tested to meet their requirements.

what are their requirement to put their logo, i guess i have to go in that certified studio with 6 mono tracks and don't have to care about encoding with ac3 by myself., but technically how is theyr encoding, is it an Ac3 as i could obtain it?

Apply for a Dolby Consumer or Professional License (http://www.dolby.com/us/en/professional/technology/licensing/get-licensed.html)