You have the ability to edit a source by clicking the 3 dots next to the source on the Sources page and choosing the option that says Edit.
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The Edit Source page gives you the option to rename the source. It also provides allows you to edit the filters that have been applied to a given source. If you need to change the actual URL or handle of the source, you will need to Archive it and re-add it.
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*Note - to archive (which is the equivalent of delete) a source, you will need to click the same three dots that allow you to edit and choose the option that says archive.