Booting from hard drive is not really more difficult that booting from CD. The only thing really important is that your hard drive has to be correctly prepared. Take a look at Section 3.3.3 to learn how to prepare it.
Start the box and enter the BOOT_ADMIN mode. (Section 2.1.1)
There are two options from there: either you know the full PATH to your hard disk device, then you can jump to next step, or you don't. In this last case, issue a search ipl to list all available bootable devices. You can also specify search [PATH]. For instance if you want to search the Single Ended SCSI bus:
Take a look at help search for details specific to your box.
Once you know the full PATH to your hard drive, you can issue a boot <PATH>. That's all. If everything goes fine, it will start booting the kernel as setup by PALO (see Section 3.3.3). Real life example: