Some more details may be required for the JM09K Matrix Keypad. I spent far too long trying to find out what pins needed to be hooked up, as they are not the same as the matrix keypads used in some of the Arduino projects I found.
Luckily, I managed to find the datasheet (somehow) that enabled me to hook everything up correctly.
Here is how I have it hooked up. I do need to replace the wires I have soldered in with a header!