For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
Depends on what exact model it is. All of them can run 10.4 (Tiger) but only some of them runs 10.5 (Leopard)
So download the 10.4 (Tiger) operating system on some torrent site, burn it to CDs (or DVD but only the newer G4’s has DVD drive), boot from cd by pressing “C” on boot up (or use boot manager by pressing “alt”), install like usually following on screen instructions.