Actually, I think the front of your case has TWO pushbuttons - On / Off (Power) and Reset - plus two LED lights - Power On and HDD activity (blinks). The function of the On / Off pushbutton is clear but it has a couple of less-known uses. The Reset button is for forcing a complete reboot of your system when it gets so confued it simply hangs and does nothing no matter what you try to do from keyboard or mouse. It is a handy "last resort", but you CAN force that action another way, so it is not entirely necessary.
The fan controller board you have controls both fan speed and the fan lights. Well, in reality it functions as a fan motor Hub and lets the mobo SYS_FAN header's PWM signals control all of its fans; the board has NO control buttons of its own for fans motors. Similarly, it also has NO buttons to control the LIGHTS in the fan frames, although it has a menu of lighting effects it can create, and you get to choose which by stepping through its choices until you get the one you want. But how to "step through"? It requires that you connect a simple momentary-contact pusbutton to its 2-pin port near the power input, and you use that pushbutton to step through light display choices. Now, the simplest way to get that required simple button is to re-purpose one that is already mounted on your front panel and easy to reach, but is NOT essential to normal operation. Hey - use the RESET button! This means you MUST unplug that button's wires from the mobo Front Panel header, and plug it into the board's 2-pin header instead. Once you do that, that button no longer can do the Reset function for you, but it DOES allow you to choose light display patterns. If you do NOT make this wiring change, you will have NO way to change the light displays of your fans. Alternatively, of course, you could buy a simple pushbutton switch and mount it yourself somewhere handy and run your own wire pair from it to the board's 2-pin header. That would do the job, too.
If you re-purpose the Reset switch as they intended, then how can you force a Reset without the special Reset switch? You use a simple feature of the other pushbutton, the On / Off button. Instead of a simple push, if you push it in and HOLD it in for at least five seconds, the system will be forced to shut down right away. Then you can release, and do a plain normal push of that button to do a normal start.