If you look at the motherboard, there will be a set of pins arranged in a 2 x 5 array. Usually colored white. That is where you will usually find the pwr and reset switches. Also, the power-led and hdd-led switches pins are located there.
The switches should be labeled on the motherboard pcb.
The pwr and reset switches are momentary contact switches which do not have polarity. If you can't find any documentation, try using the ones that look most likely to you for the pwr switch.
If you did it right, the motherboard should power on. If you missguessed, try another pair.
No harm will be done if the board does not power on.