How do I explain the faith to my friends?

Jump right in. The biggest mistake is to do nothing. You don’t need to be an expert, and you don’t need a degree in theology. Normally common sense and your personal testimony of the faith will be your best tools. If you’re asked a question you can’t answer, admit your ignorance. (The worst thing is to pretend you know the answer when you don’t.) Say you’ll have to get back to the inquirer—and then go to the library and look up the answer. At Catholic Answers we have to do this all the time, although in our case we have the library right here at our offices.