I should have specified. I was already booting while holding down "C". That brings me to:
Welcome to yaboot version 1.3.13
Enter "help" to get some basic usage information
When I enter "help", I get:
Press the tab key for a list of defined images.
The label marked with a "*" is the default image. press <return> to boot it.
To boot any other label simply type its name and press <return>.
To boot a kernel image which is not defined in the yaboot configuration file, enter the kernel image as [[device:][partno],]/path, where "device:" is the OpenFirmware device path to the disk the image resides on, and "partno" is the partition number the image resides on. Note that the comma (,) is only required if you specify an OpenFirmware device, if you only specify a filename you should not start it with a ","
If you omit "device:" and "partno" yaboot will use the values of "device-/pci@f4000000/ata-6@d/disk@0:
In the meantime, I will try the USB installation. I didn't think that was an option on an iBook. The instructions say it works on some and not on others so we'll see.