$ pacman -S bmpanel
$ mkdir -p ~/.bmpanel/themes
Download themes from here (Section Themes). Extract its content to the new created directory. Altering design patterns can be done by adapting the Template:Filename. More information on this behind the link above.
To start bmpanel automatically after the login you need to write this to your .xinitrc file in your /home directory:
# Starting bmpanel /usr/bin/bmpanel arch&