Choose the Brightpearl channel that is set on orders sent to Brightpearl.
Choose from the list. It shows the channels in your Brightpearl.
Good to know
If the list is empty, check that Brightpearl is connected. An empty list almost always means the connection, not the setting.
If a value is missing, create it in Brightpearl first, then click Clear Cache on the settings page so the list is refreshed.