an RFQ  is like a shopping list sent to multiple suppliers, asking them to give you prices for the items you need and A PO  on the other hand, is the actual agreement you place with a chosen supplier to purchase those items at a specific price and terms.

What if I already know the price of the items being ordered? I just want to write a PO and send to The vendor. 

Currently its creating and RFQ, how do I skip the RFQ and just write a PO?

RFQ is an enquiry/request to vendor to provide information related the items wanted to buy, PO is the deal document to buy including items data, requirements and any condition related.

RFQ is a request for quotation you sent to the supplier , while PO is a purchase order to the supplier after you check the prices sent from the supplier , at that time you can confirm your PO.