If you cannot find the checkout option on ReCharge it may be due to your ReCharge version.
ReCharge has two options:
If a store has (a), Address Validator can run on the ReCharge checkout regardless of your Shopify plan. Conversely, if a store has (b), ReCharge is integrated with the Shopify checkout so Address Validator can only run during checkout if you have Shopify Plus.
According to this article (Shopify Checkout Integration technical details and requirements), “You cannot convert a store back to the Recharge Checkout once it has been converted to the Shopify Checkout Integration or Migrated Shopify Checkout Integration".
(If you have the new ReCharge checkout and Shopify Plus, You just need to insert AV using our code snippet on checkout.liquid or UI Extensions).
For more information please contact ReCharge support.