Tricky one this when your new.
To make a new post you have to find forum then find which part it should be posted in, I.E off topic, iPhone etc. once found start your new topic. (This isnt a private post it's a general post to all)
To make a private post, you first have to have made 5 replies I think. Then you find who you need to PM click their name and click send message. To find the person you want to send the PM to, I usually go into favourites to locate the post then find the person in that thread. (I'm using the app) it may be different on the PC.
I think that covers it 😄 I think he does mean start a new thread myself.