X-Lite 3.0 can be downloaded from here.

1. Ensure that you have created the extension that you wish to use with the phone in 3CX Phone System first. Take note of the ID field and the password that you have entered for the extension.
   
   
   
   Configuring a SIP account in X-Lite
   
   
2. Now start up X-Lite. The first time you start it up, it will bring up the ‘Sip Accounts’ dialog. Click ‘Add’ to create a new account.

   
   
   
   SIP account properties

3. Now enter a Display name.
4. In the User name field, enter the extension number. This field should correspond with the ID field specified in the Authentication section of the ‘Add Extension’ page in the 3CX Management Console.
5. In the Password field enter the SIP password. This password should match the password configured in the ‘Password’ field in the Authentication section of the ‘Add Extension’ page in the 3CX Management Console.
6. In the Authorized User name field, enter the extension number again. This field should correspond with the ID field specified in the Authentication section of the ‘Add Extension’ page in the 3CX Management Console.
7. In the ‘Domain’ field enter the Network address (IP or fully qualified domain name) of the 3CX phone system server. If entering an FQDN, review this Article.
8. In the Domain proxy section, ensure that you have selected ‘Register with domain and receive inbound calls’. Select ‘Target Domain’.
   
   
   
   
9. Click OK to save the account.
   X-Lite showing successful registration with the phone system
10. X-Lite now tries to register with 3CX Phone System. If successful, you will see a screen similar to the one in the screenshot.
11. Now switch to the 3CX Phone System Management console, and click on Phone System > ‘Line Status’ (This is the default page). The extension should be listed, and the status should show ‘Registered (idle)’.