You don't actually need anything extra installed to play online but if you want to use a custom roster, you need to overwrite the default rosters (stored in the OrigDB and OriginalDB folders) with the custom roster files otherwise the game will take the default rosters into online play.
when i play on line i don't have the lakers with gasol, but with kawame brown. same wit boston i don't have garnett and allen. and the gameplay is slow as well can someone help me.
The game reverts to the default rosters when you play online unless you copy an updated roster to all the database folders (including the OrigDB folder under the main game folder -> database). There's a few tutorials on doing that, you might want to run a search for those.
The speed of online play greatly depends on the quality of your connection as well as your opponent's connection, as well as any firewall/security software you have installed.