How to book Qantas codeshare flights within USA and Canada?

Hi all ,
Could anyone advise the best way to book flights within the USA and Canada? Qantas website says there is an error every time I try to book e.g… Vegas to Toronto. Or should i just book on oneworld or american airlines and enter Qff number? Hoping you can help

If you can book on a QF flight number you’ll earn more status credits and points. However these flights almost always, if not always, have to be booked in conjunction with a Qantas flight to/from Australia.

In the past when I couldn’t do this through the Qantas website, I did it through a travel agent. I’m not sure how it all worked from her perspective, but if I knew the flight number and date/time she could stitch the itinerary together. Be aware that even though Qantas has partner airlines flying between particular cities, they might not codeshare. For example there’s no QF flight number available on the direct Las Vegas to Toronto flight operated by WestJet, though you’ll probably earn a few points if you put in your QFF number. If you really want a QF flight number then you would have to go from Las Vegas to Toronto via Los Angeles.

to;dr find out the QF flight numbers you want and go to a travel agent.

Thanks. I should have added it to my original QF Melbourne to LAX, but website wouldn’t let me.  Will keep investigating!