How can I remove a feed or sources?

You can either delete it from the left navigation bar by right-clicking on the feed/source:

Or by going to the feed itself and clicking the [...] and Delete - please note, this will delete all the sources in that feed/category as well.

To remove a source, go to the source in the left sidebar, click the [...] and Unfollow. You can also unfollow your sources in the Organize view: https://feedly.com/i/organize/my