First of all, set up your machine's BIOS in order to make it boot from CD. Check your motherboard's manual to see how to set up this. Upon booting up you will receive a prompt to boot PlumpOS using a specific kernel; several ones have been provided for you but, you also have the option of providing your own kernel + modules. This will be explained later in the ``Getting Started'' section. The boot menu should tell you all the kernels available for you to use; simply type the name of one (and optionally some kernel arguments) and press return/enter.
At boot-time, PlumpOS will auto-probe for network cards and, if any gets detected, it'll try and configure them via DHCP. If successful, it will fire up omdiscd on each interface a DHCP lease is received on. Currently this has only been tested in PCs with 1 network card so YMMV.
It works for myself, but may not work for you; if you experience difficulties, please email me with as much information about your system as possible -- after you have investigated the problem. (Check the sourceforge homepage for PlumpOS's mailing list, sign up and post your question with as much detailed information as possible. The openMosix-general and openMosix-devel lists are NOT for PlumpOS problems, they are for openMosix-specific problems, and if you can't tell the difference just send it to the PlumpOS list or my contact email).