My motherboard has an 8 pin input but my power supply only has a 4 pin. i plugged in the 4 pin and did a test boot and nothing happened, is it because of the power supply or something else?
Hard to say, you haven't given much to go on.
Did you have a cpu on the board ?
What board is it ? Some will work with just a 4 pin, others want that signal that says an 8 pin is connected