You can log in with your psn account. On the bottom right there is a section for quests, which almost all consist of watching a Destiny 2 youtube video.
Each quest will give you one of the unlocks which are…

Destiny 2 dynamic Theme
Cayde 6 Avatar
Hawthorne Avatar
Ikora Avatar
Zavala Avatar
Sweepstakes entry for Custom Destiny 2 themed PS4 Pro

Took about 10 minutes to do everything