There are a few things you need to take care of before you set up Corpay One's integration for Uniconta.
You need server user access to Uniconta. You will need the login details for that user when you set up the integration.
You need to have created a list of payment methods for receipts. You can read more about that here.
You need to add a default group for the vendors created in Uniconta.
Further reading
How do I connect Corpay One with Uniconta? You can learn that here.