The Metal Gear Online beta is live now, a day earlier that suppose to. But it won’t be available for download until the 17th. But evidently the PSN gatekeepers have let this 741MB download loose a day early so, if you’ve got a pre-order voucher for the beta, you may want to start downloading now. But as we all know the game won’t be able until the beta kicks off on April 21.
Here is some of the instruction and checklist for downloading

1. Open your account and be online

2. Go to Account Management

3. Transaction Management

4. Redeem PlaystationNetwork Card Or Promo Code

5. Enter code. CODE IS CASE SENSITIVE!

6. Click the MGO download icon and ENJOY

The Metal Gear Online Beta which comes in at 741mb
You need one of the 12 digit keys, as the 9 digit ones do not work

The Source: boardsus.playstation.com/