I'm not sure if you can find your family tree online "just like that". I believe you have to research name's & records. There are various sites that offer help with tracking, tracing & compiling a family tree but (of course) there's a fee. Goodluck.
There are many sites online, such as Ancestry.com, Familytree.com...., but none of them are free. Ansestry.com says that they are free, but in order to get your free trial, you need to give them your credit card number. I did not sign up, thinking that it was a little fishy. It might be free though, the best one to try out is Ancestry.com , because they supposedly have a free trial.