Please check this question first:
How much Bitcoin will I mine right now with hardware X?
Before you go through all this work, it is important to know what to expect from your hardware.
There are two options: solo mining or pool mining. Unless you have a lot of computing power (several ASICs), you should probably mine at a pool.
So the first thing to do is to sign up at a bitcoin pool. The stickies in this bitcointalk section have links for the top 10 pools. The main differences between them are the payout models and the fees. If you just want to try things out, choose one of the most popular pools like Deepbit or BTC Guild. You can then try others, according to your needs.
Now you need to install a miner. It has a simple interface, a drop down menu with a list of pre-configured pools and it is not difficult to setup.
After you install the miner, you need to point it towards your pool. So select device you want to mine with (probably your FPGA/ASIC), enter the pool URL (if you don't know what it is, check the FAQ/help section of your pool's website) and your username/password.
That's it. You can now see your progress at the pool's website.
In your specific case, you have no ASICs or FPGAs, so you will earn less than a penny of Bitcoin.