You may find it easier to download the app and manage your booking from there. There is an Advanced Passenger Information tab that should include passport information from the booking. During the check-in flow (online starting 48 hours before) it can then ask you for visa information depending on your destination. Often this is quite buggy so you can enter your passport number as your visa number and skirt around that step.

Obviously at the checkin desk you will need to ensure your passport and visa are in order but these can be different from what’s loaded to the booking previously.

The bag will be checked through all the way to Sydney. International transfer at KLIA is relatively painless, you will get spat out in a mixed arrivals/departures so can go direct to the next flight (no immigration required). Security is at the gate and starts about an hour prior to departure.