In a nutshell....
You find out if your fat is a nand or nor by checking the model number on the back...
You update to 4.82 which is the latest firmware,nothing less than that or you can brick.Make sure you update with the offical 4.82 pup on sonys website with a usb and not through the internet update.
Then you go here http://**ps3xploit.com >Domain no Longer owned by team** (ps3xploit.me =new) on your ps3 webbrowser,go to flash writer then write flash from hdd.Choose nand or nor depending on your model,getting it wrong will also result in a brick.
Make the exploit page your home page by pressing triangle and go to the tools section,close and reopen the webbrowser,last but not least you follow the instructions,get the hex file flashed to your motherboard and you will be able to install rebug as a update pup.
Once you have rebug installed you can switch to dex mode which allows more features and you can use webman.