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The person who the task will be assigned to. 

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3.

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This will be the name of the task when assigned to the user, so make it clear what needs to be done.

1.  Task Name

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 Due

The relative date offset for the due date.  Since you don't have any custom dates defined yet simply use the step change date which is the default.  In this example the task will be due 7 days after the user moves to the step.  Modify as you see fit.

4.  Must complete before end of current step

It's always a good idea to check this box because it ensures that the task is completed before allowing the user to move to the next step.

The click Submit and close the tab to dismiss the step editor.

Let's see it in action!

Literally.  Open your action