You can't. Obama has paid millions to keep most of his history hidden. You can read his book Dreams From My Father if you want to know some stuff that he is willing to tell you. To some it is pretty eye opening. To others it is not. It all depends if you believe one's past indicates one's future.
It has been shown time and time again that Obama was born in Hawaii, and that he attained and graduated from Harvard. The GOP should do itself a favor for a change and find something to be FOR instead of wasting time looking for things to be AGAINST.