A very important best practice to follow in eAutomate is to link all your service calls and sales orders that have items that need to be ordered to the P.O. you order it on. This helps assure all procedures are followed and nothing gets missed or ordered multiple times. It also helps keeps a full circle account on the order data trail from open to close. First, to make a service call or sales order have the capability to be linked to a P.O. you must set the items that you want ordered on that service call/sales order to needed or back ordered in order for them to show up as items you can link to a service call or sales order.
Then you can create your P.O. and link it to the service call or sales order by clicking the chain link icon on the P.O.
You will then get a screen your you can filter the list in the window. You can filter it by vendor (#1) and it will show you all the items that need to be ordered and have that vendor as a preferred vendor on the item record. (#2)
If you want the list to show you items for all vendors then uncheck the vendor box (#1) on the transaction window. You can also filter the item window by sales, orders only, service calls only or requests.
Also you can tell it to filter the item window by only sales orders that are on hold waiting parts.
Also see this link for automating this process through the ILC.