To place and receive encrypted phone calls with Dispel's Traceless Telephony System, you'll need to use a VoIP client. There are a ton of them out there, but we have the most familiarity with Zoiper, a free, open source soft-phone client. 

This link will take you to Zoiper's main download page. Select the version/OS that is right for you.

https://www.zoiper.com/en

1. Create a new account 

2. Enter your credentials 

3. Start calling