The B2B Order Agent Block can be installed as a block within a page, header or footer (which you can see at the top of this page), or as an App Block that floats at the bottom of all pages (which you can see at the bottom).

Sign in using the account link above (re-load the page after you've first signed in as the Shopify Flow for the store needs to run to upgrade you to an impersonator), then search for 'TEST' to try impersonating a customer. You can place orders (which come through as drafts) to see different payment terms for different companies based on who you are impersonating.