When you go to Cerulean City go through route 9 and surf down to the power plant, then go inside and the guard will tell you that a shady character has been seen at Cerulean City. Go back to Cerulean and go inside the gym and a rocket grunt will run off to the bridge, chase him and battle him, afterwards he will tell you that he hid the machine part near a rubber tube in the gym. Go inside the gym and find the machine part, then go back to the power plant and hand it to the manager, he will then give you charge beam as a reward
After the power plant starts working you go to the cave near cinnabar island and beat the gym leader Blaine. Hope it helped
Power Plant
talk to the fat guy in the power plant, near the rocktunnel. he's working at the machine
you have to have completed the power plant mission and he will be outside the power plant on the left
See below
The grass in Kanto by the Power Plant.
it is i the kanto region in soul silver after you defeat the elite 4
Battle Misty
At the Power Plant.
I don't know when but after a while the power plant
start by heading north and taking route 10 to the power plant
It's in mistys gym