how do i get under the board to replace a "switch"?

thanks.. i ended up buying a new macbook and gave him my pc laptop.. i thought i might be able to salvage this one for my grandson.. i guess not..

i meant the button that turns it on.. no.. not

i meant the button that turns it on.. no.. nothing is happening.. for a long time it would boot up one time a day .. but no more i think my husband did take it somewhere and they tried it with different ac adapter but it did not come up but the light on our adapter does come on.. steady... what i have is an original apple apple ac adapter.. they suggested it was the mother board.. it does have to come up to reset PRAM and PMU, right? in case it does.. remind me how to reset.. the battery quit showing up before all this started happening.. thanks for your help.. i got this for my husband on ebay and he's very disenchanted with macs.. which i love...