In order to get credit for a player's on field performance, you'll have to place him in a starting position at least 10 minutes before his game begins. You cannot sell players in starting positions from 10 minutes before his game starts until the opening of trading the following day.
To set your line-up, go to your roster page.
Step 1: Under the column that’s labeled edit, you will see several drop down lists that will allow you to switch between a bench spot (BN) and one or more of the starting positions (C, 1B, 2B, SS, 3B, OF, DH, SP, RP, or P). Use the drop down list to set your starting line-up.
Step 2: Click one of the “Update Roster” buttons to save the change.

After that you’ll start to earn points based on your players’ on field performance.

