The "You are trying to access a restricted page" means the file believes you are trying to access protect_Page.php directly (ie typing the address directly into your location bar in your browser).
Did you modify any of the file names? Folders? Code within any of the pages. If so those problems can be fixed.
It could be a database issue as well. Have you checked your DB and made sure your data is being properly collected?
As for adding fields and the like . . . I can help you do that. These are great products that non-coders can use, but their power is magnified five times when you know some php.
If it is not too big a deal, scrap the form you have made. Delete it from your root folder. Copy a new registration folder (not changing any names yet). Then, come back here and I (or someone more qualified than me:) will help you add your additional fields.