It would help to know which version of iChat you are using.
A New MacBook Pro is more likely to be running OS X 10.8.something.
Go to the Apple Icon top left and select the "About this Mac" item.
The Panel that shows up will show the OS version the Mac is running.
My iMac's panel.
It says I am running OS X 10.8.4
OS X 10.8.x is generically know as Mountain Lion.
In Mountain Lion Apple introduced Messages which has a different set up to the iChat versions in earlier OSes.
iChat first run
In versions 2 through 5 you get sent through a set of Start Up Screens.
These ask you for your AIM or @mac.com or @me.com names at that time.
Then there is a another screen that prompts you for your Jabber or Google ID.
There is a screen to Enable Bonjour (a way of Chatting with other Mac s on the same LAN).
Alternative for iChat
You can click through the Start Up Screens and not enter anything (it cannot tell that you have not entered an AIM name or a Jabber based name as you don't have to enter an AIM valid name or a Jabber one the first time).
iChat will now start but not show any Buddy lists
With iChat in the Menu bar chose the iChat menu > Preferences > Accounts.
This will list the Bonjour Account (everyone has this and it cannot be deleted.) although it is not likely to be Enabled.
Below this area for the list of Accounts is a Plus and Minus icon/Buttons
Click the Plus one.
This will open a new pane. (window)
The top item is a drop down.
Depending which version you have will alter what options you see.
iChat 4 and 5 will list AIM then @mac.com and MobileMe before a line that then has GoogleTalk and Jabber.
iChat 6 will also have Yahoo
iChat 3 will list AIM and @mac.com and Jabber (it did not list Google separately)
In Messages the AIM options are reduced to just "AIM" but you can still use this for @mac.com and @me.com ending IDs from Apple (That are valid AIM names)
With the drop down expanded.
Messages in Mountain Lion (OS X 10.8.x)
This will start up differently
It will ask for an Apple ID so you can "Register" it for iMessages.
iMessages is a form of Messaging that Apple have included on iOS devices (IPhone and iPads) that has been aded to what was iChat to make the Messages App.
Again if you click through this the Preferences > Accounts of the App will still show the Bonjour and the iMessages accounts that cannot be deleted.
You can still go ahead and enter AIM valid names or Jabber/Google ID s and Yahoo IDs using the Plus icon below the list.
If you have a version that means you can create and Yahoo or Google Account in Messages or iChat then you use the password that works logging into Yahoo or Google.
If you have an @mac.com ending ID from Apple make sure the password at Apple is 16 characters or Less as this is needed by the AIM servers to work.
The same applies to @me.com and @icloud.com ending IDs
However these particular "iCloud issued" IDs will not work in iChat 5 or earlier versions.
This is dues to a change in iChat 6 and Messages where by there is a Login to Apple that in turn allows the AIM server to "Read" the Password. This does not happen in iChat 5 or earlier so the names issued since iCloud started don't work.
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.4)
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