Welcome mate. Just use the @mention button on the bottom right of each post in a thread. I'm sure you can imagine what it does. You could also use the quote button as well, but I hardly use it myself. Another way you can basically use the @mention feature (assuming the person hasn't spoken in the thread yet, do this [ @mention ] without the spaces of course as well as replacing the "mention" part with their names. You'll understand when you click @mention on a thread post on what I mean. You can basically just edit what the button gives you to provide a new name.