I HAVE A VIRUS FROM DOWNLOADING 'STYLISH' HOW CAN I CURE IT?

O.K. so this is my first computer, i wanted to custimize my facebook home screen and the software "stylish" said it could do that i then learned that it tracks your history and steals passwords and does more horrid things, how can i un install this program? give me step-by-step instructions, please and thank you!!!