It's a common situation; you would like to use the Euphoria soft-phone, but the phone rings using the same device (your headset) that you are using for the phone call. In most cases the headset does not generate enough sound to alert you to an incoming call (if its not on your head) - and if it could, it would be very loud when you put the headset on!

In order to get the phone to ring using one device, and allow you to have the conversation with your headsets you need to change the default audio device. Here is a typical situation with a laptop using window 7 (the same applies for windows 8).

Go to: 

Start > Control Panel, and look for Sound

Open Sound Control Panel, where you will find a list of sounds devices. In my case I have the Laptop / Computer Speakers and the Headphones.

You will notice that that the Headphone are marked as default.

Now change the default device to Speakers, by selecting it, and clicking the Set Default button. The green tick will now be on the Speakers. When you do this, it may put a green phone icon under the Headphones section, labeling it as "Default Communications Device" (That's fine too).

Now in the Euphoria Soft-phone, go to:

Phone > Phone Settings and you will see Speaker / Headset, where the same list of devices is listed, this time select Headphones.

Basically what you have done is set the default playback device to the main sound card / speakers, because the phone can only "ring" using the default playback device, while settings the phone audio to use the headset.

Now test your configuration, and adjust the audio levels to suit your needs.