Facebook yesterday updated it Facebook Messenger Android App which added Sticker support to the app.
In last update Facebook added Chat Heads and have added built in support into the Android Facebook Messenger app for stickers but were inaccessible until now.
As it turns out, the update also consists usual bug fixes. After updating you need to open chat with anyone and click smiley to use stickers.
Download the Facebook Messenger updated version by hitting the link below and have fun.
Source: Play Store