To take a screenshot on Windows 10, simply press the PrtScn (Print Screen) button on your keyboard. This will take a snapshot of your entire screen and save it to your clipboard. From there, you can paste it into any image editing program, such as Paint or Photoshop, and save it as an image file.
If you want to take a screenshot of just one window, press Alt+PrtScn. This will capture an image of only the active window and save it to your clipboard. Again, you can paste this into an image editor and save it as desired.
There are a few other methods for taking screenshots on Windows 10 as well. If you have the Snipping Tool application installed (which comes with Windows), you can use that to select any area of your screen and save it as an image file. Or, if you have the Xbox app installed, you can use that to take screenshots of games running in full-screen mode.