What are the steps required to or the link between the item and barcode

I am using WMS

I need to use PDA scanner

Create an item AS3000

create a PO for this item

now the item is received

how the scanner will identify this item

1 - do I have to print the barcode for this item and stick it on the item and scan it?

2 - or I have to enter the barcode number of the supplier into the cross reference as GTIN and I will be able to scan the item