A task must be in a shared project before you can assign it to others.
1. Assign individual tasks.
You can assign individual tasks by using @mentions in the specific task. Type @ followed by their name. They must be invited to the project before you can assign them. The assignee will receive a notification, and the task will be listed in their personal task view and inbox sidebar.
2. Assign emails with tasks.
Any tasks listed in the email's sidebar will follow the assignee of that email thread. You'll see all the associated tasks in your personal task view by assigning that email thread to you.