How do I fix graphics?

Before on my last computer, I had all the expansion packs, (minus family fun.) and they all worked great. One day I clicked on a few buttons though I'm not sure which ones because my old computer is gone. But then the grahics were great! and i could see! so then I could actually see my sims (not just unclear sims.) But I was wondering, does anyone know how and what to adjust graphics to? (it would help alot. need for stories.)

Well I know when you're on your desktop and you right click, and click "Properties," you could set how you want graphics to look.