How to import photos from iPhone to a Mac with OS X El Capitan?
I would recommend Image Capture. It's a bit less advanced than the new Photos, but in my opinion it's simpler.

Open /Applications/Utilities/Image Capture.app to begin.

Next, select which directory you would like to import the photos to from the "Import to" dropdown.

Cmd ⌘A to select all, and hit the "import" button OR hold Cmd ⌘ and click to select a few to import. Either way, the selected images will be imported into the specified directory.

To delete all these imported photos from the exporting device (ie iPhone), Cmd ⌘A and click on the "delete" button (looks like a prohibition sign).

Side note: if you wish to rotate an image, click the "Rotate" button (looks like an arrow) and all selected images will be rotated.