Hi, according to the 2 minute tutorial there should be a JArduino option in File -> Examples -> JArduino -> JArduino firmware, but JArduino doesn't seem to be there, and the JArduino folder that it mentions doesn't exist either, so if anyone can explain why I don't have these files it would be a big weight off my chest.
We're happy to answer questions about 3rd party Arduino software here. This forum is by no means limited to discussions related to official Arduino software. In fact, this is related to official Arduino software, since you're asking about how to use the Arduino IDE.
From the unzipped folder, select the jarduino.core/src/main/arduino/JArduino subfolder. (yes, despite the name, the "Add .ZIP Library..." feature can be used to install libraries from folders as well as from .zip files).
Click the "Open" button.
Wait for the Arduino IDE's notifications bar to display 'Library added to your libraries. Check "Include library" menu' (don't bother with the "Include library" menu).
File > Examples > JArduino > JArduinoFirmware
Connect your Arduino board to your computer.
Select your Arduino board from the Arduino IDE's Tools > Board menu.
Select your Arduino board's port from the Arduino IDE's Tools > Port menu.
Sketch > Upload
After that, you should be able to follow the tutuorial instructions starting from the "Step1: Extend the JArduino abstract class" step. Hopefully they won't be so horrible as the instructions for using the Arduino IDE were.