Look at the menu bar at the top of the program window. The option to register is usually under "Help" or "About." There may also be a way to register by viewing the "Preferences," which may have its own menu in the menu bar or be listed under "File" or "Edit."
Check the program files for a registration form. The program files can be found by browsing in Explorer to "C:/Programs Files/ApplicationNameHere." You may find a text document, a PDF or a Word document that gives instructions on how to register.
Check your software package for a registration card. Some software does not come with an electronic form of registration and you can only register by phone or by mailing in the registration card.