First, you will need to get the IP address from your phone. If you need assistance please follow this article: http://support.voiply.com/troubleshooting/phone-troubleshooting/finding-the-ip-address-of-your-phone
Next, enter the phones IP address into the address bar of a web browser, press enter. the page that loads is your phones web interface. The default username is "admin" and the default password is "admin" as well. Type in the credentials and press "Login"
Next, navigate to the Accounts drop down>Account 1>Call Settings
Next, click the blue drop down button for "Account Ring Tone"
Next, select "Upload new ringtone file
Next, browse for the file you would like to use and select it. (please note these files must be in .wav format and be 500KB or less). After selecting the file you will be taken back to the call settings screen and see the file name listed
Lastly, scroll to the bottom of the Call Settings page and press Save and Apply.
Your new ring tone will play when someone calls your phone.