How to play online help plz ps3?

May be...

i registered and signed up but i want to know how to play help plz how to get in a game

when u play a game,on the menu of the game it says wat u want to play like single player,multiplayer,or online then just press the button for online,thats how it was when i played cod4 on my cousins ps3

go to your game, start playing it, go to online mode, or multiplayer,

Then it should work

u buy a game and then go to multiplayer and play online