I may be dense, but I do not see where to add the license number. In the installation instructions it says in the "Global section", I can't find this section. Besides that installation was very simple. a route to the global section or any other hint as to where to add the license key would be helpful. thanks!
Assuming nothing has changed with recent versions of Cartthrob, and Cartthrob has been properly installed you should go to Add-Ons->Modules->Cartthrob, then you should see a place to enter the licence number. (under the Global tab).
You may also have shortcut to go directly to the Cartthrob settings page in your Control Panel menu bar.