The April Android updates are rolling out, but as usual, they are doing so in waves. If you don't want to wait, you can grab the OTA file and sideload it. Where can you find such a thing? We've got all the OTA links right below.
Nexus 6P
Nexus 5X
Nexus 6
Nexus 5
Nexus Player
Nexus 9 WiFi
Nexus 9 (LTE)
Nexus 7 2013 WiFi
Nexus 7 2013 (LTE)
Nexus 10 (Lollipop)
Pixel C
Thanks: jduck, Gergely Szell