Zoom enables you to join and participate in online meetings including training. It runs on computers, tablets and smartphones.
The easiest thing to do is to visit: zoom.us/test.
If you already have the app installed on your device, this will walk you through a test meeting. If you haven't the app, it will download the appropriate version for you to install and help you take it from there.
If you feel you need a bit more, this video explains how to join a meeting:
Other useful resources: