The base game comes with two beautiful courses - Wolverine Golf Club and Florida Bay. Those courses do not need to be licensed in any way.
Add-On Courses can no longer be purchased individually - only the full deluxe edition with all courses is sold from our website while the Steam version only contains the two base courses.
If you purchased a course or course pack you will receive a receipt via email that will give you a license key for the games as well as a link to download the course file(s). The course files must be placed in the proper location to be used. This typically would be C:/Wolverine Studios/DDSPG although if you purchased the game from Steam it will have a different install path typically in C:/Program Files(x86)/Steam/steamapps/common/DDSPG
Find the courses folder and unzip the contents of the course file in that folder. You should see a Coursename.cor file and then a folder for that Course. When you go to use the course for the first time in the game you will be prompted for a license key. Copy and paste the license key from your email (dashes included) and then the course will be unlocked for all future use on that computer.