Just to clarify, are you referring to how to assign task to yourself and to others? If so, you can review this video http://todoist.com/Help/Sharing.
A quick summary on how to do it:
1. select a project to share
2. hover and select the 3 dot icon
3. click on "Share Project"
4. Invite people to shared project
5. add tasks (these tasks can no be assign to you or the other invited users)
If you meant something else, please let me know so I can help you further. :-)
Thanks, that is what I want to know.