Reassigning a Single Lead
To reassign a person manually open that person and click on the edit icon next to the Assigned Agent field:
Then select the new agent to assign the person to:
And click green icon to save your changes:
Reassigning Multiple Leads
You can also reassign many people in one go using Mass Actions.
What Happens With Tasks?
When you reassign a person, tasks created by action plans also get reassigned if they were originally assigned to the same user as the person. This is done so that tasks created for assigned agent get transferred to the new agent so they can do those tasks.
Manually created tasks and action plan tasks that were assigned to a different user, for example ISA, don't get reassigned automatically. You can reassign them manually by clicking on the task and changing assigned agent.