night shift on older Macs

You either can or you can't.

Use Night Shift on your Mac - Apple Support

System requirements for Night Shift

Night Shift requires macOS Sierra 10.12.4 or later and one of these Mac computers, using the built-in display or the displays listed:

• MacBook models from early 2015 or later
• MacBook Air models from mid 2012 or later
• MacBook Pro models from mid 2012 or later
• Mac mini models from late 2012 or later
• iMac models from late 2012 or later
• Mac Pro models from late 2013 or later

if you are running macOS Sierra 10.12.6, you should be, then you should have Night Shift.