Connect your extension using Vantact's SoftPhone Desktop Application

Once downloaded, install the application.

If you get a noticed of Unknown Publisher from Windows defender, click on "More Info" and then Run Anyways 

After the installation completes, go to your Start Menu and click on VANTACT Application Icon.

You will be instructed to enter your credentials. You can retrieve your credentials by following the tutorial below:

How to retrieve credentials:

Visit https://portal.vantact.com, and enter your log-in information.

Click on the PHONE SYSTEM TAB and then on Manage PBX

Click on settings under the desired extension

Click on Advanced

Go back to the Vantact Desktop application and enter the following information:

Portal is your domain address.
Extension: Extension is your extension/account
Password: is your portal password, not Registration.

Press Save

You should now be able to use your new softphone. Enjoy.