You can set this to either required / not required when creating a new purchase order.
In order to set up the PO component to go Admin > PO Components
Click on 'Add Section' on the Component Structure box:
Click onto the pencil icon next to the new section and this will then present you with the following box:
Here you can enter the Title IE: ACH Transfer Required and the description i.e.: If an ACH transfer is required, please enter the following details.
You will want to set this as visible in order to see this when creating a P.O
In order to create the components click on the pencil icon next to 'New Component' when hovering over the pencil icon it will say 'Edit Component'
We would suggest changing the PDF Position so that all the text lines up when previewing this and check to make it visible and appear in the preview.
Use the preview icon before clicking save and next so you can see how it will appear: