There's no wrong way to do this. In the beginning, teachers told me again, and again, what I must NOT do. Quite often that advice was contrary to my own instinct for a good story and now that I am a "more mature" writer, I wish I had listened more to my own gut and less to those you said, "YOU CAN'T."
In my writing tips, I will try to give you some pointers on how to do things including how to make up characters. But take it all with a grain of salt. Because it's not always a good idea to limit your character's experiences OR your own. In fiction, your imagination almost always comes into play, when you ask yourself the question, "What if--?"
So ask, "What if?" and then follow your instincts. Don't let anyone tell you, you can't. As Jean Auel once said, when you have written 400,000 words, you will know how to write. So spend your time writing, not worrying about HOW.