To install the eTakeoff Dimension license,

• Click on eTakeoff application icon to open it.

If you receive the window below, click on the "Install Purchased  License" button / OK

If the program opens without the window above, 

• Click on "File/Administration/Install Software License 

• Type your installation password in the "Installation Password:" box
• Type in your full name in the "Your Name" box
• Click the "Activate" button.  That will fill in the "Activation Code:" box.