Microsoft Outlook licences are an optional extra on your Hosted Exchange service, and allow you to download and install an up to date version of Microsoft Outlook on your computer.
After logging in to your control panel select Exchange from the top menu.
You will see a list of the mailboxes on your account. Select the one you wish to configure Outlook on and scroll to the Mailbox Access section. You'll see a link to download Outlook and a serial number, this will need to be entered when installing the program.