In case you've missed the announcement, Watchdogs 2 is free on PC on Sunday 12th Jul 2020.

You have to log into your UPlay account while the Ubisoft Forward event is ongoing, which starts at 19:00 GMT (that's 8pm UK time for certain Playgrounders that struggle with timezones... ).

I'm not sure whether you just have to log in and it's automatically credited or you have to go and find it and add it to your library during the event.