Although an extremely broad question.........it is one I am sure that many people who don't know how to take the first step into physical fitness ask. Though each individual is different and should take that into consideration when starting this journey of physical fullfillment; I would ask you to think about what exactly you are trying to accomplish. Strength, size, fit...etc. What do you do know? What do you eat? Are you thinking of starting at home? Do you have any equipment to start with? Will you commit to this lifestyle?
These questions could go on for pages and to get the information you are looking for........you are going to need to offer a little more information about you and what you are specifically trying to do.