Welcome to iMore! Computers are rather complex devices. If it simply "doesn't work" there could be a million things wrong. In order for us to help you we will need some more details. Here are a few questions, for starters:
1. What kind of computer do you have?
2. What operating system are you running?
3. What do you mean by "doesn't work"? What's happening? What error messages, if any, are you getting?
Thanks!