The update is available over-the-air. The build version identified as G950USQS2BQL1 and G955USQS2BQL1 for the Galaxy S8 and Galaxy S8 Plus respectively. The size of the update is 130.7MB and 127.1MB for S8 and S8 Plus respectively. It won’t take long to reach users in all regions.
The Galaxy S8 & S8 Plus users are still waiting for stable Android 8.0 Oreo update.