Workflow for PO release

Hi All,

I am new to workflow. Now I am working for PO release.

whenever PO got released I need to send a mail to vendor.

I got the standard workflow WS20000075 for this. But the problem is when I test this workflow I am encountering with an error container element is missing.

what are the settings that I have to do before triggering this workflow?

I dont have functional support here. So please help me to complete the settings first.