Click Tools> Accounts
Find the account, click on it, and click "Export"
Save the file to a disc or somewhere where you can get it to the other computer
On the other computer, click Tools> Accounts> and click Import, and import the file.
OR
Manually write down the pop3 settings that you see after doubleclicking the account you need to move.
The main parts you need:
Username, password, incoming server, outgoing server, secure authentication y/n?