To add a new task to the selected agenda item, hover over the New button and select Task.

Fill in the requested details and click Save.

To send the Task Notification to the User that has been assigned the task, choose the Send Task Notification option. Alternatively, see the Article on Sending Agenda & Task Notifications, to send the task at a later date/time. 

Related Articles:

1. Adding Tasks - Field Explanation
2. Editing Tasks
3. Send Agenda & Task Notifications
4. Task and Action Log Management
5. Contributor - Accessing 'My Tasks'