This blog post explains how to set up Gmail so it will be able to initiate and receive voice and video calls.
- Download and install the Google Talk Plugin from here.
- Restart your browser, preferably Google Chrome.
- Log into gmail in your browser.
- In the top right corner click on the cogwheel icon, and then select Mail settings.
- In the Chat tab, set up the settings of Voice and video chat.
- Click on Verify your settings and make sure it works properly.
- Save the settings (Save Changes).
- Select a friend in the chat list, open a chat window. In the chat window there will be a phone or camera icon, with which you can start the voice or video chat.