Easier way: if you see Peter Francis’ icon somewhere on the forum, just click on here and as a card opens you’ll see “Message” tab on it. Click it nad it will open messaging pannel directly, however the text of the post you’ve sent message from will be quoted in the PM. Delete it and use your own text instead (if you don’t want quite to appear of course).
For more guidance “how to” on the forum, go to this thread where you can find more or less everything you need. It’s not strange you are a bit “lost” since the software was quite updated in this time and many of the instructions need revision too but they could be helpful anyway.
Oh, and … Croeso nol!
For the name changing … yes, @petermescall has got it right, you’d need to contact @aran for that.