First you'll need to look up a list of what PS3's can be Jailbroken.
Then if yours is able to be Jailbroken you will need to buy a E3 Flasher to downgrade your PS3 to update 3.55
After you downgrade, I'd recommend finding someone who already has jailbreak and ask them do they still have their JB File and get them to email it.
Update you PS3 from the USB that has the JB File on it and with your PS3 on 3.55 with the JB File, your PS3 should restart and Jailbroken.
Ask someone who is already a Modder about Spoofer and Multiman
Spoofer lets you play online to where PSN thinks your PS3 is running update 4.66 (which is current update) but it is actually running 3.55
Multiman helps you to control the Jailbreak. This is where you turn on and off the jailbreak so if you want to mod, or if you want to play legit. That is where you get your free games too.