And I answered that you don't, unless the stories are very specific (ancestor's name, or exact place on pedigree). You just narrow down which branch of the family they are supposedly in, and research that line as you would any other. Child leads to parent. If you hit a dead end, search for distant cousins in that line and see if they have the same stories.
On a similar note, whenever the subject of genealogy comes up (which it often does with me), a friend of mine always mentions that her great-grandmother was a full-blood Cherokee. She and her children seem very proud of that fact. The girls get dark tans in the summer and the boys like to hunt, all due to their Native American roots.
None of the living family had ever met this ancestor, and my friend said she wanted to find her death certificate. She knew all the family names, so I said I would check around. I found the certificate, which listed the ancestor as "white," and gave it to her. She and her husband assumed the family was hiding their mixed race on the document, but it didn't appear that way to me.
I did a little research, and found the ancestor's grandparents - all Irish. Not just Irish, very OLD Irish. Going back further, it seems her family came to Georgia from Ireland in the 1780s.
I thought that was kinda cool, but not so sure her kids would appreciate it as much. Crushing their grandma's story. So I never had the heart to tell my friend the truth, but one day I will.