As you can read in the article, you must do the following to enable this support:
1) Install the Cumulative Update (which requires you first install SQL 2008 SP1. Remember if you have not installed SQL Server 2008 yet, you can use
support to install RTM, SP1, and CU 2 all in one setup execution).
2) Enable trace flag 845 as a startup parameter
3) Ensure the service account for SQL Server has the
Locked Pages in Memory
privilege set. This is not required if the service account is LOCAL SYSTEM.
As part of this change, we have updated the following KB article (note the article is updated to indicate it applies to both SQL Server 2005 and 2008) that has many more details about Locked Pages, Working Set Trim, and the possible ramifications of enabling this for 64bit systems.