Q: .... start talking to people?
A: In the top right, you'll see a grey button: "New Topic". Click that. Better still, go into one of the following four areas: Stall Catchers, Alzheimer's Disease, Suggestions Box or The Coffee Shop and then click "New Topic".
Q: .... start talking to people in a discussion someone else has started?
A: Go to that discussion. At the bottom right there will be a "Reply" button. Click that.
Q: ... report a problem?
A: It depends what sort of problem it is, but in Stall Catchers (for the citizen science game) and the Suggestions Box (for everything else) there are pinned threads to describe the problem. Click "reply" in them, or start new topics in those areas.
Q: ... send a message to someone?
A: At the very top right you will see your profile. It will probably be a circle with the first letter of your name. Click this. You will see your name come up, and below that a row of words, the third of which is "Messages" with a button that looks like an envelope.
Q: ... give myself a profile picture?
A: Click your profile (at the top right). You will see your name and then a row of words. The last one is "Preferences". Click this. The fifth item you will see is "Profile picture". It's easiest to choose something from your computer. You can, of course, just stick with the letter you are given.
Q: ... report a spammer or malicious user?
A: I'll edit this as soon as I've found out myself.
Q: ... please suggest more.