If you have a single developer license, simply download Understand from www.getunderstand.com and enter the Single Developer code after the installation. No other steps are needed. If you have lost your code, you can send an email to email@example.com to have us resend your code.
If you have a new client, simply install Understand from www.getunderstand.com and point it to the license server when prompted. If you are moving the license server itself, follow the instructions at scitools.com/floating to get the almhostid for the new server. Then send that id to firstname.lastname@example.org along with the license.dat file from the old license server, and we will send a license file for the new server.