How to convert Purchase requisition (replenishment purpose) to purchase order

How to convert Purchase requisition (replenishment purpose) to purchase order?

Always tag the AX version(for now i have updated it as AX 2012) and provide brief description of your issue/requirement.

How the demand is fulfilled now?

I can see the way the demand is fulfilled is determined by master planning,

https://technet.microsoft.com/en-us/library/hh271540.aspx