Normally if you are replying to the post/comment immediately before your post, you just add a new comment/post - its not like reddit where there are sub-threads of comments, its just one stream.
If you really want to make sure the person you are replying to will read your response, you can use the @mention system, that will ping them to let them know you want their attention.
How should it be used?
Quotes are for referencing a specific small part of a post/comment, particularly if you are replying to a long post and you think people wont understand exactly the thing you are responding to.
I apologize if this is alr answered somewhere else!!
No problem, its second nature to some people, but its understandably less normal if you did not grow up with forums!