4.2: Restrict RSS Feeds From Showing In New Content

I have an RSS feed that exports content into a specific forum.  How can I NOT have this content show in the Unread Content Screen?

I think what you're after is what (was) in the older series (I only mention this as its easier to understand) the equivalent of "View new posts: Block Forums"

4.2.x go to ACP > System > Content Discovery > Streams > Click on the pencil icon on the right for the 'Unread Content' item, it is usually the top of the list here.

On the page that opens about the third setting down is called 'Content Types' change that from 'All Content' to 'I will choose'

Check all the boxes as appropriate here, for the Topics one when that's clicked an extra section will appear under the list of forums, and you can uncheck the 'All' box and pick all the other ones.

A pic may help a lot here...