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.
If the items are not successfully added after the code has been activated on your Steam account, please try to verify the integrity of your game files. You may follow these steps to do so:
Open your Steam Library > Right-click on Battlerite > Properties > Local files > Verify integrity of game files
These mounts are activated in the original Battlerite only. In order to use them in Battlerite Royale, please first 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.