This can be done online in 5 easy steps as depicted below or through the Team Selection Card (Through a registered agent, see here for more details)

Step1: Join a Game
In the New Game window select one from the list of available games to play and then click the Join button.
Step 2: Select Ur Team
Select a squad position (e.g. Goalkeeper) to see a list of all the available players in that position and their monetary values.
Select the Player you want from this list and move over to the next position…Defender
Repeat the same process until all your squad positions and substitutes are filled.
After all positions are filled, click on the Save Team button
Step 3: Register Ur Team
If you are a new user, you are prompted to Register or Login if you have already registered.
If you clicked on Register, you are redirected to the registrations page. Enter your details and next you should check your mail box for your password.
Click on Continue…