ON INTERRUPT works fine if you do not care if the event is not acted upon instantly. ON INTERRUPT is pretty easy to use.

If a interrupt is time sensitive you will want to use ASM interrupts, there is an example in the manual, but ASM interrupts can be tricky.

The best of both, easy and fast are brought together here.
http://darreltaylor.com/DT_INTS-18/home.html

You will still need to have your data sheet open...