The process of setting up a Simplify account for payments is described here.
Connect the mono shop
Once an account has been set up, the mono shop must be linked to your Simplify payment gateway account.
This is done here in the mono editor: SHOP -> PREFERENCES -> PAYMENT
Select the Simplify payment gateway, and then input the information needed to connect the shop:
For Simplify payments you need to insert the “Public key” and "Private key". This information is found in your Simplify account.