how to pay Marriott online instead of POS machine

when i book online, there are two way to pay the hotel
1. non-refundable
usually pay directly on the internet

2. refundable
usually not pay on the internet
check in staff will ask for my card and let me pay by POS machine

my question is, how to pay online rather than on the pos machine because i can get more points if i pay hotel on the internet
thank you a lot