Hi,
 
How can I setup moneybookers as the payment processor?

Its already defined as a payment system in V3.6.
 
Go to Administration >Orders > Payment Systems and find MoneyBookers (number 43 here). Click Active to "Yes". It then goes towards the top of the payment system list.
 
Now in "Edit Payment System" change the parameters to the ones supplied when you signed up for a MoneyBookers account following the inatallation notes.
 
Finally change the parameters in the other tabs to suit your system.