A great PS3 tutorial has been posted on YouTube by ChrisTechTV. Chris explains in detail and also shows you the steps involved to downgrade your PS3 from 3.50 firmware to 3.41. Its a cool 15 minutes long but if your new to all this its worth the trouble sitting through it and even maybe taking notes. Note that while Chris is using *cough* pushing the E3 Card Read to downgrade, the steps involved here are pretty much the same for all USB dongles that can downgrade.

Source: YouTube