You can receive Magic Moonlight Carpet, Magic Royal Carpet, Sweet Candycorn and Twitchicorn by going to follow.battlerite.com and following the instructions.
You will receive a code that should be redeemed in Steam.
Launch the Steam client > Click the Games Menu the upper left corner > Choose Activate a Product on Steam > Follow the onscreen instructions.
These mounts are activated in the original Battlerite only. In order to use them in Battlerite Royale, please download and start Battlerite (free-to-play, available on Steam). Once you have started Battlerite, the mounts will be activated on your account and can be used in Battlerite Royale as well.