Activation is the last step in acquiring your Thea Render license. After completing the registration process, you should receive an email with the final license file in .dat format.
Open the License Wizard:
In SketchUp: Extensions > Thea Render > License Setup
In Rhino: Thea Render > License > License Form
In Cinema 4D: Thea Render > License…
Click on the Browse button and select the license file (.dat) that was sent to you.
If everything went fine you should be able to see Activated at the top of the window.