Hi Samratnav27! :)
In addition to what you already got from Karan, which is a complete example setting up all you need...
especifically for the Vendor Approval Workflow, you can find an standar template in NAV:
Just go to Workflows , New Workflow from Template and select the "Vendor Approval Workflow".

In there you have an standard template you can start with.

I hope it helps :-)