You don't.

See the "INITIALIZATION FILE" section of the readline manual (`man readline`):

> Readline is customized by putting commands in an initialization file
> (the inputrc file). The name of this file is taken from the value
> of the INPUTRC environment variable. If that variable is unset, the
> default is ~/.inputrc. If that file does not exist or cannot be
> read, the ultimate default is /etc/inputrc. _When a program which
> uses the readline library starts up, the init file is read, and the
> key bindings and variables are set._