It wasn't still released officially (follow Dona Sarkar on twitter for official news). If you can't wait join the Insider program via Settings, and choose the Release preview ring, the safest. We are already in Redstone
It just got released, so check for updates, it should be there. If not, it should come soon (ish). And if you don't want to wait, just join the Insider Preview program on any ring, though Fast ring will soon get RS2 builds.