For an email, note, task or piece of work to display on someone's to-do list, it must first be assigned to a team member.
Emails & notes
On every email or note, you have the option to assign it to yourself or assign it someone else. You can do this by clicking on the assignment icon, or via the options menu "..." by selecting assign. The options menu allow you to select the to-do period and other details.
Work
Every time you create a piece of work, it will have a person assigned to it (as a default, the creator of the work).
Tasks
Finally, you can assign a task from the work it belongs to.
If you assign the item to yourself, it will be put on your to-do list. If you assign it to a colleague then it will be placed on their to-do list.
Assignment panel
Every time you assign an item, it will display an assignment panel below, showing the assignee and by who it was assigned from.
If you expand the to do item you can see:
who is it assigned to
the to-do period it currently sits on
the due date
the status of its progress
All these details can be changed by clicking on them.
You can also reassign items as you see fit.