Everything about your plan and your usage lives in Configurations > Subscription and usage. Livy charges through Shopify, so billing goes together with your store’s.
In Configurations > Subscription and usage you see your current plan, whether it’s active and the date of the next renewal.With “Update plan” you can change it or view all the plans whenever you need to.
Your program’s usage is measured in credits (one credit equals one email sent). On this same screen you see your balance, and the full details are in the “Credits” guide.