You can either sign-up via the competition page in Kraken Pro, or, follow these steps to get started:
Check your eligibility
Make sure you are verified to Intermediate or Pro
Create a Kraken Pro account or sign in
Visit the  Kraken Pro competition page to accept the Futures Terms & Conditions
Meet the minimum futures trade volume requirement of $2,500 USD (for example: equivalent to opening five separate $50 USD trades)
The competition entry will automatically unlock, and once you’ve registered you’ll get $10 USD credit as a trading collateral to start competing right away. You can also  add your own funds into your Futures wallet (follow instructions for Kraken Pro)