By paying ? If yes, by which payment method ? Paypal, CC, E-Gold ..?
Can you please link me to a explaining thread or tell me here...

Had you bothered to browse the site ... just a little ... in the Suggestions section, the one right above this one, you would have noticed that the last post made there dealt, in part, with your question.

Donate thread

Currently, you earn your way into VIP membership by contributing things of value (quality proxy lists (hopefully exclusive ones), knowledge of proxy related items, etc., etc.).