An Activation Key is used to modify the license information (e.g. increase number of licenses).
Select the option License Viewer in the TAB Help
Click on the button Transfer License
If you got an Activation Key via e-mail or fax, you can enter the key within the screen Administration, TAB Misc, Show License Information.
If the evaluation period has expired, select Show Licence Information (see screen below) and then press the button Activation Key.