How to connect a joystick to a de2 board

That is rather difficult, but it can be done. The de2 has a adc, but I don't remember how many. Another way is giving all the data parallel, this involves using external adcs. then connect the x&y axis outputs to the dac, the z axis is a button I believe, and thus can go directly to a GPIO pin, with an external pull down resistor. The ground to ground and the supply to a supply pin, but be carefull about the voltage here, it should not exeed the max ratings of the gpio pin AND adcs.