The first step would be establishing a genealogical connection to the family. Have you actually traced your family tree? You have to establish a family connection (and often only in the legitimate male line) beyond just a name.

Once you have done that (which can be long, tricky, but also rewarding in itself) and if you really want to go all out into the technicalities then the college of arms would be the people to contact.

http://www.college-of-arms.gov.uk/