If you’re on Xbox One or PC, but you didn’t have access to the Call of Duty: Black Ops III multiplayer beta, fear not, because now you do, as mentioned by Treyarch on Twitter.
The Xbox One/PC #BO3Beta is now open to everyone on those platforms. LET'S DO THIS!!!
— Treyarch Studios (@Treyarch) August 28, 2015
To be more precise, there’s a caveat on Xbox One, as you need Xbox Live Gold in order to get access.
— Xbox (@Xbox) August 28, 2015
You can find the PC version on Steam and the Xbox One version directly on the console in the marketplace.