Yes, you can! If you have Viking Points, but not enough to pay for a full top-up, you can combine them with one additional payment method to complete your purchase.
For example, 2 Viking Points = € 2 calling credit. If you want to use this to top up your SIM card, first select 'I want to use Viking Points to top up' and then a second payment method below to pay the remaining amount.
Keep in mind that you can only select one additional payment method to complete the top-up. The combination of a bank transfer, a text top-up or an automatic top-up is not possible.