Susan, here's my non-expert advice on how to get started;

Put Zoom.us in your URL box. (Note the dot after Zoom)

Fill in your e-mail address.

Click on "sign up for free"

Follow the prompts down the rabbit hole. What you are doing is setting up a free Zoom account for yourself so you can call and join meetings in the future.

It worked for me.
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When it's time for the sing-a-round, get your camera, microphone and earphones (if any) plugged in and ready.

When it's 8 pm in London and 3 pm in New York, a link to the session will appear here. Copy the link into your URL box, and it will take you to the session. Click 'join with audio' or something like that.
It's pretty clear what to do. This is one hour before the official start, but people like to chat.

The sessions are pretty long, so don't worry if you miss the start. I plan to be there.