These steps will walk you through how to elect to receive your W2 electronically. Please note that you can only do this during a certain time of the year (usually September through December) You will want to watch the ESS alerts which will notify you on when you are able to opt out of receiving a mailed W2 and instead receive it electronically.
Login to ESS
Click on "payments"
Click on "view or update W-2 election"
Check the box that says "do not mail the w-2 form"
Make sure you hit "save current selection"