Once you have initiated your search and found the relevant purchase orders you can tag them, make notes, and add them to your calendar to follow up with them. 

Start by clicking on the description of the Purchase Order in your list of line items. 

Once you have this opened scroll to the bottom of the page and you'll see the tag option, a notes box, and an add to calendar button. Make sure to save any changes you make when you're done. 

The tags you add to purchase orders make them searchable so that you can find them later or search for them at a later date.