In Messages on the iPad you need to be using an Apple ID (which you probably are)
You can then iMessage (the form of Apple Chat Messaging that is used) to other Apple IDs or iPhone numbers.
They have to be using iOS 5.5 or higher or OS X 10.8 on a Mac. ( A Mac could be up to OS X 10.8.2 if updated iOS devices could be up to iOS 6.0.1)
You then needs either WiFi access or a Data contract and an iPad that can do at least 3G (some have SIM cards)
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously