How do I set up the Supporter plugin to only allow supporters to write posts and pages after a free

Hi there,

Have been reading the forums for a few days and deciding which plugin to use to monetise my new site, and have also read and re-read the post about how Edublogs has tried to make money in various ways.

I have decided to use Supporter and have installed it, but I can't find the option to let only supporters create pages and posts as below:

If you wish, disable the "Write Post" and "Write Page" pages on non-supporter blogs (i.e. you must be a supporter to blog)

This is taken from the info on the Supporter overview page so it seems to be possible, could someone let me know how to do it please?

Sorry if I've missed something simple!
Lee