According to the official news on Blizzard website, during free weekend players will have access to full roster of 28 heroes and 18 maps, variety of modes, including Quick Play, Custom Games, and the Arcade. Players will also have the ability to level up, earn Loot Boxes, and unlock a variety of different customization options. To play Overwatch, you need to:
- Download Battle.net app
- Log-in or create a new account
- Click on Overwatch icon in Blizzard app and press "try for free"
This game is free until July 30th. Enjoy!