Need the info in this thread but receiving "access denied" message

There's info in the following thread I've used before but need again, but I'm getting an access denied message:

https://www.dell.com/community/Desktops-General-Read-Only/Second-Monitor-will-not-work-via-HDMI-port-Dell-Inspiron-3847/td-p/4498175

There's another thread on the same topic but the solution was to buy an adapter, which I'd obviously rather not do since there's a working solution that doesn't require purchasing anything. I just can't remember what the solution was.