Followed one after another.
Standard process is :
- One employee is linked to one supplier (link is done automatically via PRAA in XK03 accounting view of supplier you have the pernr filled).
- Transaction PRFI to create data to be posted (amounts on supplier accounts...). Depends on your process but generally done by HR guys.
- Transaction PRRW to create posting in FI. Same depends on your process.
- FI documents are created, there is a debt on supplier account so it must be paid. Payment is done by transaction F110 by FI guys.
Hope this helps 
Regards
Mathieu