You can't really follow people.
The site is easier to navigate if you use the mobile site, rather than the desktop site. Go to the bottom of whatever page you're on and flip it to mobile site.
The search button in the bottom right-hand corner will let you search for a particular poster.
DMing is done by going to a comment and looking at the three dots in the bottom right. Clicking on that will take you to the DM function for that particular poster.
Protocol for answering specific people is to hover on their name so you can copy and paste it into your post. A star either side makes it bold. If you put an @ in front of it (no stars), it bolds it and automatically sent them an email to say they have been tagged, if they have subscribed to that function.
The three dots next to particular post itself is useful for book marking. Next time you open that thread it will automatically take you to the post you have bookmarked.
The 'I'm on' button at the bottom of your screen will automatically show you all the current threads that you have posted on.
Lastly, on the desktop version, go to the top of the page with the drop-down arrow and go to customise. You can colour in your posts, and that of the opening poster, to make navigating easier.