It varies from laptop to laptop but in most instances (at least that I've seen), the Print Screen key won't be it's own key. That is to say, it will "share" its function with another key on your laptop and so you'll kind of have to toggle between the key's primary function and secondary function. I know it sounds kind of confusing, but hear me out.
The Print Screen button is usually abbreviated in some way. On mine, it says "Prnt Scrn/SysRq" in blue right underneath my F11 key.
If I were to press the F11 key (the key's "primary" function) alone, it wouldn't do print screen but it would do whatever F11 usually does. So to use Prnt Scrn, you'd either have to press and hold down the Ctrl/Fn (in my case, because it's also in blue)/or some other key before pressing F11/Prnt Scrn (and then release both) in order to do it.
This copies whatever screen you happen to be on. Once you've copied the screen you want, you'd open up Paint (which should already be on your computer) and then just paste (Ctrl+V or right-click and select "paste") the image there and save it onto your computer. Once it's saved onto your computer, you can click on it, and then it should open up in some sort of picture viewer program on your computer so that you can edit it however you want. Hopefully this isn't too confusing!