The Super Mario Run sticker pack can be downloaded on an iOS device, but it is not listed in the dedicated Messages App Store nor can it be installed on a device running an iOS 10 beta or the iOS 10 golden master.
When iOS 10 becomes available to the public tomorrow morning, the Super Mario Run sticker pack, along with other sticker packs, will be accessible. We expect to see iOS 10 released right around 10:00 a.m. Pacific Time on September 13.
Unveiled at Apple's September 9 event, Super Mario Run is an upcoming Mario-themed endless runner. In the game, Mario runs forward continuously while players jump to collect coins and avoid enemies, and there's also a "Toad Rally" battle mode for competing against other players.
Apple is promoting Super Mario Run heavily, including offering a new "Notify" system in the App Store that will let players know when it's released. According to the Super Mario Run Stickers app, Super Mario Run will see an official launch in December of 2016.