You must be an Administrator within Gearbox and have a Xero account created before proceeding.
In Gearbox, click your user profile on the right-hand side of the screen (1) and select Settings (2) from the drop-down:

On the left-hand side of the screen, click on Integrations (1), a new page will load:

Scroll to the bottom of the Integrations page until you locate the entry for Xero. Click the Connect to Xero button (1):
Pop-ups must be enabled in your browser to continue.

A new window will appear asking for your Xero credentials, enter them and click Login (1):

If the login / connection was successful then you will receive the below page:

If you receive an error message then please contact Gearbox Support for further assistance.
Once the Integration is complete you will now have access to the Export to Xero button on Purchase Orders:

This will create a draft Purchase Order in your Xero system for further processing in there. You must still close off the Purchase Order in Gearbox otherwise it will remain ‘Open’ indefinitely.