You have 2 ways of using Ottspott for making & receiving calls, send SMS, launch audioconferences:
Inside Slack by launching bot and slash commands. This will trigger a link and once you click, it will open a Chrome browser tab.
With the Ottspott desktop app that you can download here together with the click to call extension: https://chrome.google.com/webstore/detail/ottspott/jifpnmbeiicjhambhempmloabbimecpn. The desktop app will allow you to see which of your Ottspott team members are online, have access to a call feed, and much more. Please check the Ottspott Desktop App section for more details.