Hi Linda, I tried a relationship search between you and Andrew Johnson and found no relationship. Then I checked your profile and tree and see that you have not added very many ancestors.
I think what you need to do is add your grandparents and their parents. The more generations and details that you add the more likely you are to find relationships to other profiles on WikiTree.
As you add ancestors for whom you know the details and get a little farther back you will probably start to add a great grampa (for example) and find that he is already here. Once you connect an known ancestor of yours to the big tree, you will begin to see all sorts of ancestors!