Sage Payment Solutions (Sage Exchange) offers your business more ways to accept and process payments, so you can provide your customers with a variety of ways to make payments for products and services.
Note: this payment method is most suiteable for North America and allows to accept only the payments in US dollars. If you want to set up SagePay gateway for UK, please refer to this article: Sagepay
1. Sign up for a merchant account at www.sagepayments.com
You will receive a Merchant Id and a Merchant Key (M_Key Number). Save them to use on the next step.
2. Enter your Online store control panel and proceed to Settings → Payment.
Choose any payment method, click "Change" link and select "Credit card: Sage Exchange". Fill in the settings form with the id and the key you obtained after registering at Sagepayments site.
Save the form, enable the payment method and click "Save".