If you will have your accounts receivable in Younium and keep track of payments, you would want to add payment methods for bookings and accounting. Normally there is a structure for this in your accounting system. Consider distinguishing Younium payments from other payments by setting up a specific payment method and bank account to separate you subscription payments from other payments received.
Go to Settings>> Account Receivables >>>Payment Methods
Then press ADD
Name your method and give it a Description, then add the Financial Account for payments, the Exchange Rate Gains and Losses, and Bank Fee accounts. If this will be your default payment method, hit the Default checkbox.