It's a limited offer, so make sure you make the most of this opportunity — jump on the PlayStation Store and hit "Download". Go on, it's free.
For a limited amount of time today, you will be able to download the Beta straight from the PlayStation Plus section of the PS Store.
"We will not be sending emails or voucher codes for this; it will simply be available for you to download straight to your console.
There's more information on the PlayStation Blog should you require it. Click through here for that.