Hi,
As you said, scenario is simple. But you need to understand the process flow of the template and logic which are there to calculate the overall ratings for the KPI and appraisal.
Go to OOAM - Create a Categoty and appraisal template. Under that create KPI as criterion group with Free enhancement. Select the respective columns required, roles, status flow to start the appraisal document.
Regards.
Srikanth