Follow the instructions for installing Amahi on i386 starting at the third instruction ("start a terminal").
Install time will depend on your network, but both the install.11.10 step and the amahi installer took around 10 minutes for me(using an USB hard disk). Of course this also depends on your network speed and on speed of the servers.On SD card this will take substantially more time.
== Install Ubuntu on BeagleBoard/BeagleBoard XM/BeagleBone ==