Please follow the below steps to Install and Configure Xero in Vtiger
Installation:1. Click on
Menu icon
2. Click on
Extension Store3. Search for Xero

4. Click
Install and confirm by clicking
Yes.
5. Click
OK in the pop-up for a successful installation.
Configuration :
1. Click
Xero from the list view of
Organization/Product/Invoice/Payments.
2. Click on
Authenticate your Xero account button and get redirected to Xero login page

3. Enter the credentials to login to the Xero account.

4. After you login successfully, choose your Organization created in the Xero account.
5. Next, click on Allow access button to authenticate you Xero in Vtiger to get back to Vtiger CRM
6. To sync the existing records, click on Sync now button and view the sync log.
Refer :
Xero Sync