Petter, you need to first have your paypal account... If you have then login to your account and under Merchant Tools Tab look for the link "Donations". It is Accepting Website Payment. Then you just have to fill up the form on the details about your donations.
After filling up the form, click Create button now.. Then you will be provided with the code.. Just copy-paste thsi code to your page where you want the button to appear. When you go live the button will already work. So when a user clicks on that button he'll be directed to the Paypal site to place their donations.
Glad you got the requested info, Petter ... I took the liberty of removing that "Referral Link" from your Namepros Signature, as well. :gl:
All the best!
-Jeff :wave: