Add your parents to wikitree, then grandparents, and keep going back a generation at a time, including sources for each profile. Include sources from the Record tab of family search, as an example, not from the family trees. If you find family trees, include the sources found on the tree. If the tree has no sources, then it isn't reliable. Eventually, you will find an ancestor on wikitree already. If you think you have William Brewster or anyone else as an ancestor, verify all of the branches down to your parents and make sure they are all on wikitree. Then, your family tree on wikitree will show that direct relationship.