Top menu >> Setup >> Select process >> Workflow tab

You can create action types which allow you to set conditions such as who can edit or trash the action. If you add an action and select a type the conditions will apply that are setup. 

Click + Add an action type

Type: Name the action type. 

Date mode: select one of the date mode options.

Assignee can  edit: select what the assignee is allowed to edit. 

Action trash by: select if the assignee is allowed to trash the action. 

See also: