Service entry

Hi Gurus,

When I go to document flow of my client,

The doc flow is: Std Order - Delivery with picking Qty zero, (Batch no also exist in delivery) - Service entry - PGI - Invoice - Accounting doc.

In some doc flow is: Contract (VA41) - Std Order - Delivery with picking Qty zero, (Batch no also exist in delivery) - VT01N - VI01 - Service entry - Invoice - Accounting doc

I dont have any idea of creating Service entry. When I go to T Code ML81N, I find only the option of Purchase order.

How to create service entry. Pls help me to understand the flow.

I have to create test data in DEV Client.

Regards

Rakesh