Fundraising: How to hide wdf checkout form to unlogged in Users

I'm developing on WAMP and using simple donations. How could I hide the checkout form (form class=wdf_checkout_form) from unlogged in Users? I know a small amount of php and have played a bit with fundraiser.php but haven't got a solution as yet. My aim is to allow unlogged in viewers to see the fundraiser but only allow logged in members to make a donation. Hoping it's something simple I've missed. Thanks.