It says to use
bind '"\C-r": "\C-ahh -- \C-j"'
to bind to Ctrl-R; the "bind" command can be used in the shell directly. Alternatively, you can put "\C-r": "\C-ahh -- \C-j"
in your ~/.inputrc. hstr --show-configuration >> ~/.inputrc && . ~/.inputrc
You can run just hstr --show-configuration to check what will be appended