Step 1: Go to Inventory & plan Items
Step 2: Select Manage Stock
Step 3: Click on "Add Stock Without PO"
Step 4: Select the Vendor Item using the Drop down.
Step 5: Click on "Receive Stock"
After clicking on "Receive Stock" it would take you back to your current stock page. This page will give you the list of Vendor Item which are "With out PO".