Using the combination of buttons
All manufacturers have their way of making screenshots through the combination of buttons, and is that not everyone has the same, as in the case of Sony for example have no home button, so the combination is different.
In the case of Samsung just have to hold down the home button and the power button simultaneously for one second, made this capture will be taken by the sound of a shutter to know that the screenshot was carried out properly and the image is saved in the gallery.