Step 1: Get the game
You will need to get the original game in order to play online. Below you will find various stores where you can buy it.
Step 2: Download the matchmaker
The matchmaker is an application originally made to replace the now-extinct EA matchmaker to allow you to easily find other players to socialize and to play games with. It also adds a whole lot of other features such as: custom maps, rankings, 8 player support and much much more. The matchmaker is essential for playing online.
Step 3: Create an account
In order to log in to the matchmaker you will require an account.