There are many resources at your disposal to find biographical information. Here are a few.
When might you use the catalog?
If the person in question has been active for many years, it is likely that books have been written about him or her. This may be a novelist, a politician, or a scientist. Remember that when a book is written about a person, a Library of Congress subject category for that person's name is created. So using the Subject search in the catalog is a good way to find books about that person. For example, here is a screen shot of the results of a Subject search for books about Theodore Roosevelt. You will see that there are even sub-categories, which will help you refine your search for books on certain aspects of Roosevelt.