In order to find out what line you come from you can start with your father. Find his birth certificate through your local registry or from a site such as Family Search or Ancestry.
On his birth certificate it will state the father and mother (your grandparents) and usually their location of birth. You continue to do this and add this information to your wikitree.
If you hit a roadblock, you can corrospond with the community of people who are researching your surname/needed surname.
You continue to research, reasearch, research. I even recommend searching google or similar search engine for something like "your surname" & "date of birth". That method has helped me when I hit a snag on someone before.
There are tons of methods, sites, and people out there who can help you in your search for your family tree; all it takes is time and dedication on your part to move farther back. I have been stuck on a single individual and can't find any information on him to move back for over a year. Just keep your head up and push through it.
If I can help you further in anyway, please let me know.