Chosen Solution

ok so i have a 2007 macbook motherboard im gonna use it with a portable monitor so one thing i dont have a power button and some ppl said to me to solder a switch/button on the motherboard but i dont know where to solder one but thanks i appricaite the help

For this model I believe the power on pads (marked with a power icon) are located below the fan:

You can just solder a basic button & two wires to those and you’re set.