You will need to set up the Connection between the CRM and Xero so that you can synchronize the data in the 2 systems.
To do so, you will first need to go to Tools > Xero > Configure connection to Xero.
If you then click on 'Connect to Xero' you will be taken to the Xero login page.
Enter the Login details for your Xero Account.
Then make sure the correct organisation is chosen in the dropdown.
Click Authorise.
Once the Connection is approved by Xero, you will be taken back to a landing page. You can close this page and go back to the tab which you have the CRM open in.
Next Step: Xero Database Area Setup