Open the sticker picker in any channel on 『✺₪𝑴𝒊𝒄𝒕𝒍𝒂𝒏₪✺』 and pick RAAA.
Sending it on other servers or in DMs needs Discord Nitro.
To add it to a server you manage, download it, then open Server Settings → Stickers → Upload Sticker. Discord takes PNG, APNG and GIF files up to 512 KB.