The platform doesn't have advertising plugins... How do I add them and how do I use them to display ads?
There are tons of extensions across the various communities,
(and I believe most of them work with all builders)
Have you tried searching for one?
https://community.appinventor.mit.edu/search?q=Ads%20extension%20%23extensions%20in%3Atitle%20order%3Aviews
search for ads extensions in the extensions directory App Inventor Extensions | Pura Vida Apps or here in the community
Taifun