se agrega el server en /etc/pacman.conf
[arch-games]
Server=http://arch.twilightlair.net/games/x86_64
Para 32 bits
[arch-games]
Server=http://arch.twilightlair.net/games/i686
despues con un pacman -Sy para sincronizar los repositorios
Update: los servidores estan muertos, aqui los nuevos servidores
64 bits
[arch-games]
Server = http://pseudoform.org/arch-games/games/x86_64
32 bits
[arch-games]
Server = http://pseudoform.org/arch-games/games//i686