Purchase Requisition workflow

Dear all

I am new to designing a workflow. I have designed a simple Purchase requisition workflow. Start → Approve Purchase Requisitions → End…In Approve Purchase requisition level down having a setup for user Admin where purchase requisition currency to b AED

When I am done with a purchase requisition , I get a submit button. On click of submit button , the status changes to In Review. I am not sure how to move further with the next level . The status In Review has to be changed to Approve. In the sense I wanted to do automatic approval so that later on I want it to convert into Purchase order