Before exporting bills to Xero you will need to setup Inventory Items in Xero, please see the Creating Inventory Items article for more information.
1. Ensure that the supplier is linked with the accounting system  (their name must be selected in Acc. Dropdown list. If the supplier is not in the list you will need to export them first, see the article on Exporting Suppliers for more information.
Then ensure that each line has an Acc. Item  and Tax Status  selected. Finally click Export 
2. You can verify the export by checking the Acc. Total field  and if required check the status between the two systems by clicking the E  button to update this total.
3. If required view the bill in Xero.