To download the 7-something GB beta (if you fulfill the above conditions), follow these steps:

Highlight the Uncharted: The Nathan Drake Collection game icon Select ‘Overview’ Select the Uncharted 4 Multiplayer Beta Tile and press the X button to begin your download from the PlayStation Store

The beta will run through till December 13 starting today, and none of your progress in the beta will be carried forward to the final game. It is also introducing some new features including a new loadout item- ‘Mysticals’, which lets player use some supernatural powers seen in earlier Uncharted games. Alongside Mysticals, Sidekicks is another new feature that the beta provides. Sidekicks is essentially a loadout option that spawns an NPC ally, each with a unique skill to help you or your teammates along.

Though not much time has passed since the beta went live, certain issues are already springing-up. Naughty Dog, the developers of the game, posted a tweet acknowledging the issues with matchmaking. The tweet is given below.

Members of the developing team will also be streaming the multiplayer gameplay live on Twitch on December 8 and 11.

Uncharted 4 is expected to arrive mid-March next year only for PlayStation 4. 

Uncharted 4 beta now available for PlayStation plus members - 57