To access the Checkout settings, you first have to log in as Host.
Then you will have to go on the Checkout page. To do so, either click on a Checkout button if you have one or directly on the item(s) on top of your screen.
Enter the Editor Mode by hovering on Edit Page and then clicking the Edit This Page button.
You will now be able to enter the settings: hover on the little Gear icon above the Checkout module and click Settings.
The Settings appeared as a popup window. It can be enlarged if you click on this button, on the top right corner:
Go on the AO_CheckOut Settings tab and scroll down to the payment options available and their settings.
Here are the settings available for POLi.
Plans & Pricing
About Acumen Online