I assume you mean RSS feeds.
You can generate an API key for a user account on your site in the admin section. Then you can just append it to any URL like so:
http://meta.discourse.org/latest.rss?api_key=KEYHERE
I should note there are security issues with making that api key visible to users. If someone has it, they can do anything that the underlying user account can do. It would be much better to fetch the RSS server side using the key then only exposing the resulting feed.
Also, be especially careful not to generate an “All Users” key for this. If someone gets that key they can do anything as any user on your site. So just be extra careful 