https://www.gamespot.com/articles/destiny-2-pc-beta-pre-load-now-available-for-some/1100-6452889/

Right on schedule, Destiny 2's PC beta client is now available to pre-load, at least for some players. People who pre-ordered Destiny 2 on PC can now pre-load so they can start playing precisely when the beta goes live on August 28.

People who pre-ordered a digital copy need only press "Install" in the Battle.net app to pre-load. Retail customers have to go to bungie.net/redeem to redeem their code.