Aftermarket case trying to figure out the wiring

if the motherboard is atx and the power supply is atx then the mb connectors should be marked on the mb and power supply. the mb side you will need a magnifier to read the small print. they will be in a line together somewhere near the lower corner of the board, in a straight line. usually rst is reset - hdd led is hard drive led and the square 20 pin conn, goes somewhere near the processor. if you have at board or powersupply it won't work they both have to be the same form factor. there are others and not knowing the case or ps i cant give you more info.