The ability to add customers to Recharge depends on the platform your store is using:

Shopify Checkout Integration

Merchants on the Shopify Checkout Integration cannot manually add a payment method to Recharge. Shopify requires all new subscription customers to go through the checkout as the initial payment token creation needs to take place within the Shopify checkout.

During migration, customers can be added to Recharge if they have an existing payment method on file with Shopify.

Recharge Checkout on BigCommerce

Merchants using the Recharge Checkout can manually add customers as outlined in the Adding a customer to Recharge guide.