It's probably easier to explain the situation because I know there are multiple ways in which "about" could be used.
I am speaking with a friend and I tell them I went to a meeting. The next thing I would like to say is "the meeting was about leaving Japan"
To generalize this grammar point even more I guess I'm asking how I would make I sentence that say "this is about this"
I have a super basic understanding of Japanese so I'm trying to learn as I message/slash talk to people.