Please teach me something

Take the digital out from the CDP. That is the only way to do it. If you don't have one you are out of luck. Analog output(s) don't have a signal the DAC can decode.

Yep, as Newbee said, the inputs on a DAC are all for a digital signal and, depending on the particular DAC, those inputs may be coax, optical/Toslink and/or USB.

CDP's have two main components inside one box, a transport to pick up the data from the CD and a DAC to convert it for output from its analog out jacks. If it also has the provision for digital output the internal DAC is bypassed and the digital signal made available at the digital output jacks, commonly coax and/or optical.

The digital signal going to the DAC may come from a CDP, Squeezebox, Airport Express, Sonos or anything else that's got the output.

The output of the DAC is left and right channel analog signals, suitable for input to your preamp/amp.

Just to oversimplify, DAC stands for "digital to analog converter". We don't listen to bits and bytes or a series of 0 and 1 (digital). We listen to a continuous waveform (analog).

The information on a cd is digital, and the DAC converts it to analog. As stated above, cd players have built-in DACs. If you go from the cd players digital out to an outboard DAC, you bypass the cd player's DACs and you can alter the sound of the translation from analog to digital. Like other equipment, each DAC has its own sound (although many differences are subtle IMHO).

A computer soundcard is also a DAC, for example, because it converts digital to analog.