The Call of Duty: Black Ops 4 PC open beta will be available to all Battle.net users starting Saturday, August 11 at 10 am Pacific. Those who pre-ordered or received a beta code from Activision, however, can start playing today—the early beta access period began earlier this morning.
There seems to be a bit of confusion about it, which is fair, because it's not well communicated. While it's nice that you can pre-load, it doesn't help the confusion that anyone can download Black Ops 4 in Battle.net right now even if they can't play it yet.
If you did pre-order, you should be able to play. If you were sent a code, that also ought to get you into the early access period on Battle.net. (That could be a Battle.net code, or possibly one for redemption at callofduty.com/blackops4/beta.)
We'll be playing this weekend and we'll let you know what we think next week. Sadly, we won't get to try out the Blackout battle royale mode during this beta—that's being saved for another beta in September.
Call of Duty: Black Ops 4 releases October 12. Check out Andy's preview from June for more on this year's CoD—which is actually quite different, having ditched the traditional singleplayer campaign.