Uhhh
You move your mouse (the arrow) onto the Blockland.exe file (the one with a big B) by moving the oval shaped thing next to your keyboard (or by sliding your finger over the touchpad if you use a laptop) then you press the far right button on your mouse (the oval thing) and it will open a menu.
You then move your mouse to the Rename area and click the left button on your mouse (again, the oval thing) and now type in blockland.exe with a lower-case b (using your keyboard) and press return or enter (the key with an arrow below backspace) and then run your dedicated.