TLDR: The business referring you to Thirdfort requires your passport as photo ID for verification. To start, select the 'Passport Check' task from the list, then follow instructions to confirm you have a passport and scan its photo page.
I've been asked to provide my passport
When acting on your behalf the business that referred you to Thirdfort needs to verify who you are. To do this they have asked you to provide your passport as a form of photo ID.
Starting the passport check
To start the task please select the 'Passport Check' task from the task list. You'll then be given a brief introduction to the task and what you have to provide.
Providing your passport
Please press the blue option to 'begin.' After this, you'll then be asked to confirm you have a passport. Please select "Yes I have a passport." You'll then be asked to scan the photo page of your passport. You can read more about completing this stage here.