Edit Photos location on 'Photos'

The new Photos app does not (yet) support adding or editing location info. See for example the Being able to assign location to an image in Photos? discussion in this forum for more about this -- people ask about it daily.

Apple has announced that the next OS X version (El Capitan) will support this & a few other frequently requested features:

In Photos, you can add locations to a single image or an entire Moment, and sort albums by date or title. Additionally, you’ll be able to download third-party editing extensions from the Mac App Store℠ and access them directly within the Photos app.

However, it is unknown if these features will be added to the Yosemite version.