First you make a network connection for the PS3 you must already have a internet Service Provider from DSL or Cable Broadband Internet and the hardware and devices needed for either a WiFi or Ethernet connection. For many people with a PC already connected that means purchasing a router and connecting it to your cable or DSL modem. On the PS3 you go to settings>network setting. With an ethernet cable from a router it will search and find your connection, then if you do not have an ethernet cable it will seek out the strongest WiFi signal.
How do I connect the PlayStation 3 computer entertainment system to the Internet? has been added as a related link and it is to the Playstation Network SupportChat with our AI personalities
Some PS3 games have online play. When you own the game, have an online connection, and the game disc is in the machine you can play online
Some PS3 games have online play. When you own the game, have an online connection, and the game disc is in the machine you can play online
To go and play online on your PS3 is free. The exception of course is that you do of course have to pay for an internet connection. Also certain online services on PS3 do cost money, such as netflix.
There is no two player online for mw2 on ps3 or xbox 360
You need the game in the PS3 to play it online, then it is an option available if you are also able to go online