Arch set the keyboard to german or french

Press ALT+F2 and type: setxkbmap de
or setxkbmap fr


To enable locale
To enable or disable them, the file /etc/locale.gen is used. It contains every locale you can enable, and you have just to uncomment lines you want to do so.

So #pt_BR.UTF-8 UTF-8
becomes pt_BR.UTF-8 UTF-8
Remove the # before the locale.