Awesome, congrats!!!!
On the portal there's a Zoom link. That's where they'll hold the intro session, and that link is also your "home base" throughout the day - if anything goes wrong, just go there, and they'll sort it out for you.
There are additional links for the actual interview portion, and they'll walk you through this in detail tomorrow. It's an MMI interview, so you'll go through 8 different stations, with a different interviewer/prompt at each. You get 2 minutes to read the prompt and I think 8 to answer. Don't try to just talk for 8 minutes straight; they have follow-up questions. You ARE allowed to take notes, so have a notepad or something handy! You'll get a 5 minute break between each session to re-center yourself. The way it's set up, each new station should automatically open up in Zoom, but if it doesn't work, you also have links you can click.
Don't worry if you have technical problems! They've built in extra time to accommodate for that and everyone is VERY nice! Don't stress out, it's very low-key. You got this!!!