In reply to Dan's PM:
Dan, if the issue is how to reply to the emails you get letting you know there has been a reply to a
thread you either posted or commented on, you need to click the link in the email to go to the thread. I don't think replying to the email does anything! Once you are on the forum post, scroll down to the "Post Reply" button (circled in the first attached screenshot). Click that button, and it opens a white box you can type your reply into. Then once you've written your reply, click the "Submit" button, circled in the other attached screenshot.
As you managed to use the PM system, I am sure you will figure this out too!