To change the store currency of your Etsy store, go to Shop Manager > Finances > Payment Settings > Currency.
You can read more on how to do this and how this affects you in Etsy's Help Center here.
Please remember to go back to your Gelato dashboard and sync the store to ensure all updates are synced and reflected on the Gelato end. If you skip this step, Gelato will be creating new products using the wrong currency.
You can change the billing currency of your Gelato account as well. Read more on how to do so in our article How can I change the currency in my Gelato account?