How to always start emacs with Relative Line Numbers turned on by default

[J191]

In Emacs 26.x, How do I get Emacs to start with Relative Line Numbers turned on 
by default ?

I tried to use C-x h, then clicked the menu item and the help showed the 
following

<menu-bar> <options> <showhide> <display-line-numbers> <relative> 
runs the command #[nil "\300\301!\210\302\303!\207"
[menu-bar-display-line-numbers-mode relative message "Relative line
numbers enabled"] 2 nil nil] (found in global-map), which is an
interactive compiled Lisp function.

So tried adding the command into init.el as

(menu-bar-display-line-numbers-mode relative message "Relative line
numbers enabled")

How do I make this work ?