Look on the board. There should be a positive or negative symbol on there I would think. Check both sides of the board.
If nothing else, look for videos or pictures of that ESC installed, and see if you can see where they go.
Ok. I found this video, and stopped at a point where it kinda showed...
Awesome. Furitek give you that? So they were there at the event? That is too cool.
Looks like that Furitek Igmelon kit works with your stock ESC. So it will disable your current ESC, but still use the receiver in it. So you can still use the stock radio.
So there is no magnet on the body? If not, I am going to guess that's it in top of that body mount. That looks like it may have been glued to the body, and the glue ran down to the mount. I wonder if there is another magnet in a pocket in that plastic mount.