Open your wallet, sync with the blockchain, go to the debug console and type setgenerate true -1 to use all the cores of your CPU.  Replace -1 with 1,2,3,4.....and so on if you want to specify how many cores you want to use (generally if you are using the PC while you mine, not a bad idea to leave at least a core open for your normal activities).  Then.......wait.  Thats it.  Old school solo CPU mining is all we got until an external miner is created.  Depending on the difficulty and the power of your CPU, you can go days without finding a block so be patient.