The usual approach is to add a landing page or custom component in your portal and load the external app in an ‘iframe’.
this only works if the external app does not block framing with headers like X-Frame-Options or Content-Security-Policy frame-ancestors
- update the portal tp add a landing page to in App Studio / Constellation so users can log into
- use a custom DX component / iframe wrapper to render the external print application URL
- assign that portal to the required operators/access group so users logging into that portal land on the page that contains the embedded app