Take the user manual that came with the device. Usually such guidance clearly explain the procedure. Sometimes there can even be a detailed images or photos. Read the manual and find on the printer the appropriate button.
If the instruction for any reason missing or written in an unknown language, try to find the power button yourself. Usually it is located on the front of the housing of the printer, and has distinctive externally icon or the name "Power". Sometimes the power button has the shape of a classic lever-switch located on the side or back of the case.
If you are sure that the button is correctly detected, but the printer still does not work, then check whether the device is connected to the network. Trace the wire from the electrical outlet to the device, check the connection of all cables. Make sure the outlet is working, and the room where you are, there is electricity.
Do not neglect this advice. Maybe you just forgot to include the network filter.
Some of the printers start their work only if the ink cartridges are installed correctly. Check, checking the user manual if they are in your device.
If the above tips do not help, it is likely that the device is really faulty. In this case, you should contact the technical support of the manufacturer of the product you purchased. Or you can, put the printer in its packing box, to take his purchase back to the store, detailing the sales assistant the problems.