This page links from General Softphone Information.

Helix Telecom offers free documentation support for Zoiper 5. Previous versions of Zoiper are unsupported.

NOTE: Zoiper is a paid application. The free version of Zoiper is capable of making and receiving calls only. The paid version of Zoiper is approximately $40€ (40 Euros). Zoiper supports Windows, Mac and Linux. Helix Telecom support is limited to Windows clients only.

How do I install Zoiper 5 on Windows?

How do I enable Click-To-Dial feature with the Chrome Browser using a Zoiper softphone?