Setup > Custom > Mobile App
On the left top, click and select the warehouse
Main Menu will appear,

Click on Receiving, the receiving page will appear

Click on the Purchase Order, On the Purchasing Page we can select the PO through :
SCAN/ENTER PO # OR ITEM
Select PO By Vendor
Find PO By Vendor
Find PO By Item
select PO from any of the ways, SCAN/ENTER ITEM or directly select the Item from the List
SCAN/ENTER LOT then click on Enter Lot
A page will appear to Enter the Quantity
It will also shows the BACK ORDERED QUANTITY, QUANTITY REMAINING then Enter the Quantity in the ENTER QUANTITY Column and click on Enter Quantity
SCAN/ENTER BIN or click directly from the list to select the Bin
A message will appear PO successfully created