If you are creating a new purchase order, there will be a field called purchase order notes that you can fill in at the time you are creating your purchase order. Follow the instructions here to create a new order.
If you are editing a draft or existing order, there are two ways to achieve this:
Through the use of editing cells, you can make widespread changes to purchase orders in line. Through the baseline Open orders base view, there is a column included titled PO Notes. Click into the cell that needs to be revised and add the comments directly into the cell. SAVE EDITS and issue the revised purchase order to your supplier contacts by clicking SAVE AND ISSUE PO.
From the order details page
From either expanding the purchase order from open order details or locating the purchase order in global search. Scroll down the Order Details information on the left-hand side and click into the section titled Purchase Order Notes. Add your notes and then click ISSUE REVISED PO.
Note: If this was a previously issued PO, all supplier contacts with access level set to Orders, Notifications will be notified of the added note. Those with Orders access will not be notified, but will still be able to access the order when they log into Anvyl.