According to the license agreement you can have your XLN Audio products installed on two computers at the same time. Simply run the XLN Online Installer on your second computer and you will be prompted to register your computer before you go further with the installation process, this will add a second computer registration to your account.
You can delete any computer registrations you're no longer using to make room for new machines by logging in to your XLN Account, going to View My Account and clicking the Computers tab.
If you then want to move one product from these two computers to a third computer, you can.