When choosing a subscription, you can add a discount code. Navigate to the Settings tab {1} in your space and click on Subscription {2}. Select a payment interval {3} and choose a plan {4}. This will take you to the checkout page.

Enter your credit card information and click on the Add promotion code {1} tab and input your code if available.

If you can not see the Subscription tab, make sure you’re logged in as the owner of the Space or as an Admin with permission to update billing and payment information.