Once you’ve graduated from your @Training Wheels, you are able to create and use your own custom monster blocks.
Avrae reads bestiaries from Critter DB. If you want to import your own monsters for use with the bot, you need to create an account here and create them first.

NOTE: When parsing attacks, Avrae will read the initial damage value as well as one additional damage value specified within the same sentence. All other values will be ignored, and Avrae will not roll any saves.
Once you’ve created all your monsters, you can add them to Avrae by running !bestiary import <link>. Keep in mind that you can have only one active bestiary at a time. You can view your current active bestiary with !bestiary and swap to a different one with !bestiary <name>. Update your active bestiary with !bestiary update.