Well then it's a poor manual. Anyways, on a typical modular power supply cables will be labelled as well as the cable receptors on the power supply. It should not be very hard figuring out which goes where. Usually you can't even plug something in the wrong place by accident, as there are slight physical differences in the pin support edges. Many cables are different configurations of pins so it should be straight forward. Just don't mix up the CPU cable (called EPS12V or ATX12V) with a graphics card PCIe connector (may be labeled VGA or PEG).