Example: suppose you are interested in law and you are located in Memphis. You would choose law as one topic, and you would choose Tennessee as the locality for your primary focus. You can add as many topics as you want. At this stage of the beta game, you have around 150 or so topics. From my own personal experience, you are better off choosing just a few primary topics in order to skew results in a meaningful way.
In the beta version, only the first page of results is personalized.