None of the regular cruisers have answered, and I've only done land crossings into Canada, but here's what I know.
Your profile, which you can set up anytime, includes: basic ID information (name, address, etc.), passport (or Nexus) number, vaccine types and dates, and a photograph or PDF of vaccine evidence. Be careful on the last of these items. For an entry last year (before they introduced permanent profiles) I accidentally uploaded an email confirmation of vaccination rather than images of our actual US vax cards, and this caused delays and a "random" test at the border.
When I first started using ArriveCan (we go to Canada a half dozen times a year) I did a dummy entry ahead of time to figure out what the process would be - similar to a trial booking on a ship to find out what cabins are available - then bailed out before I did the final "submit". I'm sure you could do the same for a cruise ship entry.
For each entry into Canada, you enter: date and time of entry*; port of entry; address you'll be staying at in Canada. I imagine the ship's name would be sufficient? certainly we've never entered a hotel room number. You'll also be asked a few questions about your current state of health - "Any COVID symptoms?", etc.
* They won't allow you to enter a date further away than 72 hours. For time of entry I've just made my best guess.
I'm not sure if they do "random" testing for ship entries, but if they do: the process is VERY cumbersome and they will phone you relentlessly afterwards to confirm you have completed it. Even after the results have been delivered.
I use scare quotes around the word "random" because my wife has been "randomly" tested on three of our last four entries.