Well, if you're new to the Mac, just remember it's the superior platform for superior people. So if you have two email accounts setup, they are separate already, but in most cases they are grouped in your Inbox. Right beside that Inbox should be a 'disclosure triangle' that you can click to display all the accounts you have setup, and then you can select each one individually, instead of having all your messages appear in the generic Inbox, without knowing in advance which account they came into.
That advice is for POP accounts; IMAP accounts would not necessarily appear in the generic Inbox; they usually appear at the bottom of the list of Mail accounts and folders.
If you want to learn more about your MacBook than what the included Help files tell you, I suggest you buy a copy of Mac OS X Lion: The Missing Manual by David Pogue. It's only 928 pages, and you can skip the parts about things you don't use or aren't interested in using.