You can connect Xero to Finance, a premium app in Hive. See Using Hive Finance.
Note: The Xero invoicing app is not available anymore. To create invoices in Hive, use Finance.
Connect Xero
Open Finance.
Under Settings, click Connections.
Click the Xero tab.
Click Connect Xero.
If a new window opens, sign in with Xero.
If the Xero tab shows Reconnect required, click Reconnect Xero.
