Chris Pramas has posted a guide to using the Pirate’s Guide to Freeport with 4th Edition.  It covers levels, races, classes, and the points of light concept in general.  As Chris explains, Freeport is a rules free campaign setting, so fitting your 4e game into Freeport should be relatively painless. 

Freeport is Green Ronin’s signature city setting with classic fantasy elements, cruel-hearted pirates, and Lovecraftian horror come together in the rum-fueled metropolis known as the City of Adventure.