Hi Seannie
Using the app, you'll see several 'check-in' tasks. One task is for identification. It will ask you to photograph your passport and take a pic of yourself, and ask for your address and such. Takes about 3 minutes if you have everything together. The next task will ask you about vaccination (brand, date) and take a photo of your Vacc. record. Takes about 2 minutes.
The next task is to choose an arrival time on departure day.
I'm pretty sure the other steps can't be completed until you take your pre-cruise test.
Ed