Follow the post link above but to sum it up.
If you are on firmware 3.55 or lower, then download a custom firmware (try google search kmeaw 3.55 CFW), place it on a USB under PS3>UPDATE (the name of the file should be UPDAT.data install it through the update option on the ps3.
I recommend searching the forum before asking questions. This question in particular is answered multiple times a week, and the answer can be found on threads which are stickied.