If you are using a smartphone or tablet, you can usually project the video on a big screen by connecting the device to a TV or projector that supports screen projection, or by using wireless screen projection functions such as AirPlay, Miracast or Chromecast TV sticks.
If you are using a computer, you can connect the computer to an external monitor, projector or smart TV, or use a wireless screen projection device (such as a Chromecast TV stick) to project the video on a big screen.