If you want to capture a specific part of your screen, use the good ol' Snipping Tool. Search "snipping" in your search menu and open it. Then click "New" and it'll tint the whole screen slightly white (it might do this automatically when you open the program, so you may not have to click "new"). Then drag and select the region you want to capture.
Oh and when using Print Screen, if you hold the Windows key and press PrtScr, it'll automatically save the screenshot to a folder in your Pictures library called "Screenshots" (at least thats what it does for me).