You can only play the Custom Course by using it when you create a CC Tournament.
I also believe you can create as many Custom Courses as you wish but in order to actually use them you also need 1 Course Builder Pass for each time you wish to use them. Course Builder Passes are available to buy in the Pro Shop or you can win them in Clashes.
I'm not a CC owner so this is only how I think it works. Hopefully an actual CC owner or someone who knows for sure how it works can add to this post.