Assignment Rule new assign

Hi
Just started using ERP next domo for installation. Not a IT major. Can I know how to automate To do list once a task is made by assignment rule, how can I make the status closed instead of “cancelled”,
So I made a doc type and assigned roles and add level permissions for easy access for the level users. Also made a workflow for the custom doctype.
when it comes to the assignment rule I assigned workflow_state ==‘state’ codes for assignment condition and workflow_state ==‘state’ codes for assignment condition. Instead of using this method how can I automate the tasks for this rule

Please check this.