How to import m4v files into iTunes 12.2.1.16 on Mac OS X 10.1.2.16?
When adding an .m4v file, or other acceptable A/V type file extensions, to iTunes either by drag and drop or using File > Add to Library... the file is added to Home Videos under Movies.

In a fresh install of OS X, in the image below, it shows the available tabs when selecting Movies in iTunes.  Note there is no Home Videos tab.



In the image below, after adding a video to iTunes the Home Videos tab appears under Movies and shows the added video.