The answer is that you most likely are not.
The latest release of the Bitcoin client (v0.3.23) no longer includes any mining component. Mining has advanced to where for it to make sense you need the right hardware, need to run the appropriate miner software, and need to use a pool.
The combination that works for you is unique based on factors such as what hardware you might already have or are willing to buy (or, more importantly nowadays, … able to acquire) and what your skill set is.
Hope this helps!
Written on 14 Jun 2011.