Hi OldTrog,
You can separate the feed sources in one of two ways.
1. You can set up multiple pages using different shortcodes for each source. For instance, in one page you can use the shortcode [wprssaggregator source=”21″], and in another using [wprssaggregator source=”35″], where 21 and 35 are the IDs of the feed sources. You can get the IDs from the Feed Sources page. They are listed under the ID column.
2. Since you are using multisite, you can also set up each site for each feed source. This however can be a bit of an overkill, since all you will have on each site is a single page with a shortcode for that feed source. If you opt for this method, you can make your sites look very simple and clean, by making the page with the shortcode the homepage.
We recommend you use the first, since you can better organize the pages for each feed source in your site navigation menu or sidebar. People can choose the feed source they want to view from there.
To show all the feed items of all feed sources, you can simply use the shortcode [wprssaggregator]. This will aggregate all the feed items into one page.
Hope this answers your question.
Miguel