Here is an article about SharePoint Form Configuration. Basically, you need to modify the web.config of the content site and central admin site. But you should keep the central admin's role provider . Then you need go to central admin to change the web application's Authentication. One web application may be accessed in different zone, for example intranet and internet zone. You can config intranet access site to use windows authentication, and config the internet access site to use form authentication. But The web.config files of all access site need be modified to know the information of form authentication.</p>

One thing to note is that you need to enable the PeoplePickerWildcards like the following.






Another thing is make sure the application pool account can access the user database.