Title pretty much says it all. The video shows a button to push to add an email as a task, but no such button shows up.
Oh - I figured it out - One has to add a task first, and then can add the email to the new task.
We're sorry for the inconvenience. We've noticed this issue and indeed the link will appear either if you add a task first, but to avoid this, you could also try to just open any email in your inbox and once you open 1 mail, then this link should also appear in Todoist. We will try to address this issue in future updates.