This is a very interesting piece of kit. A PDF of the schematic is here http://www.wvshare.com/downloads/accBoard/5-IO-Keypad.7z
Because this board contains keys and a joystick you'll need to be just a bit more careful with your programming logic. But in general what you need to do is...
1. Wire up the board. Leave board pin 1 unconnected (it doesn't do anything). Connect board pin 2 to arduino GND pin. Connect board pins IO1 thru IO5 to arduino pins 2 thru 6 them in any order.
2. In setup()
you'll need to enable the internal pullup resistors with pinMode(pinNum, INPUT_PULLUP)
3. Create a readAllPins() function that does a digitalRead() on each of the arduino pins 2 thru 6 one at a time.
4. Create a scanKeys() function that does a digitalWrite(pinNum, LOW) on each of the arduino pins 2 thru 6 one at a time and in order. Then for each arduino pin that you digitalWrite(pinNum, LOW) call your readAllPins() function and store the values into a variable.
5. Inside loop(): Call your read function first and if any pin is low that means the joystick is being used. You can tell which direction by the arduino pin number that reads low. If all pins are high then call your scanKeys() function to see if any buttons are being pressed.
You can't use the keys and the joystick at the same time and there's no debouncing. All that can be fixed later once you are more familiar with what I wrote above.
Let me know if you need more detail. I wouldn't mind playing with the code for this.