Once you click the "+ Create" button on desktop or the "+" button on mobile and choose the type of post you want to upload (Regular, Album), you will see a window where you can set the access type to "Paid Access" or "Pay-to-Unlock Post".
Paid access means that only members of your club with paid membership can see your post.
Pay-to-unlock means that members of your club with paid membership can see your post and non-members or free members of your club can pay a fee to unlock the post and view it.