Once you've purchased your first paid seat(s), you can manage billing-related tasks through Stripe. To do so:
Click your user icon in the upper right
Navigate to the Billing and Team page
Click the Manage on Stripe button in the top right corner
You'll be directed to the Reclaim payment portal on Stripe where you can:
Click Update plan to add or remove seats.
Manage your payment methods and billing information.
Cancel plan to end your subscription.
View your invoice history.