I gave a customer an $10 account credit.

[Anchorfusion030]

It is showing up in her account but not when she checks out. How does she use/apply it? 

[LuffyOnePiece]

Hi @Anchorfusion030 ,

Customers can use their store credit as a payment method on your store only when logged in through new customer accounts. To support customer login using new customer accounts, use one of the following options:

Set your customer accounts login experience to new customer accounts in your Shopify admin. Learn more about switching to new customer accounts.

If you use classic customer accounts, then in your Shopify admin, go to Settings > Customer accounts > URL. Copy the URL that gives customers access to new customers accounts. Provide your customer with the URL, and let them know that they must log in using this link to use their store credit.

Here is the documentation for store credits.
https://help.shopify.com/en/manual/customers/store-credit

Thank you