To activate Diller together with Front Systems cashier, you as a customer must first send an order to Front Systems confirming your agreement to upgrade to Front Systems XL Subscription.
Do that here: https://frontsystems.wufoo.com/forms/w41406u1wd2r46/
Once this is done and the connection is set up, you will be able to proceed with creating vouchers, etc., in Front Systems that work together with Diller.