Purchase Agreement Link while Creating PO from Purchase Requisition......

Dear All,

I am using Purchase Requisition from the system. while the purchase requisition is approved system as functionality to create the Purchase Order directly for the approved PR.

For the Item I have received  PR I had already made Purchase Agreement with some vendors.

So Can I link My Purchase Requisition to Purchase Agreement while directly creating PO from PR........?

Or is there any way after creating the PO I can link the same to Purchase Agreement....? 

Regards,

Jinesh Shah