display is extra large

for some reason my screen images are huge and I can't figure out how to get back to normal size. It must have something to do with display size but don't know how to find info on that. The "help" function doesn't help.

Just switched over from pc when given this machine.

System Preferences, Display.

You'll find System Preferences under the "Apple" menu (the one on the far left side of the top menubar).