Start by connecting the laptop to the mains via the correct charger/poewr pack. This should come with the new computer. Make sure the mains in on so the computer can start to charge.
Having done that wait about 10 minutes.
Now press the [ON] button on the laptop. Your machine should now burst into life and (assuming it has all the bits inside connected and is set up with an operating system) it should be ready to work with.