Booked an AC ticket on United and when I log into to manage my reservation on Air Canada, it won't let me update my personal details, which I'd like to do and add in my Known Traveler Number (KTN). This'll then let me use the TSA Precheck lane on my US --> Canada flight; I'm also hoping to update my frequent flyer number, as I've got *G status with SQ and right now it has my basic UA details listed.

Any tips on how to do this without a lengthy customer service call, or is that unavoidable? Happy to do so at check-in if these updates can be made then, but recognize they may not be ...