Information about getting to Frankfurt from the aiport is given on its official website. If you want to use public transportation, there is also the possibility to use a regional bus to the next train station, and take the train from there. You can search for such connections on bahn.de - use "Hahn Flughafen Terminal 2" as starting point of your journey.
There are luggage lockers at the Frankfurt/Main main train station. They are coin-operated.