I forgot how, sorry. I actually did my undergrad at UofT, so I already have my UTORid. Not sure how it works at the graduate level, though if I had to guess, you would probably need to get your T-Card so that you can use your UofT account. And in that case, getting your T-Card requires going to Robarts Library in person.
There's an option to buy a 8-week membership at the Housing UofT site (guest account) for $24, in case you need to use the site before you get your UTORid!