This feature is only available to customers on the instant plan.  To upgrade from daily/hourly plans, go to My Account > Change Plan.

There's a few steps to enable purchase orders, which are outlined below:

1. Enter the purchase order setup

In the top menu there is now a new option for Purchase Order Setup under the Accounting Link menu.

2. Map your account codes

At the top of the purchase order setup screen, there's a link to map your account codes.

The account codes setup now has options for purchase orders and freight/courier on purchase orders.  Set these to the accounts in Xero you want to use.

For each individual account code mapping, you can now also specify whether it's also valid for purchase orders.

3. Setup the other purchase order options

On the purchase order setup, there's five different options you can set.  Once you're happy with the setup, make sure you check the purchase order module active and click Save.  Purchase orders will start coming through to Xero shortly.