Examine your CD player and locate the RCA jacks. These will be simple to identify because there will be one white jack and one red jack. It will say "Line Out" somewhere near these jacks. White represents the left stereo channel and red represents the right stereo channel. Depending on the model of CD player, there may only be a white jack, although this is rare. Insert a converter into each jack; the color of the plug doesn't matter on your converter, but note which channel is which.
Plug each of the 1/4-inch jacks into the back of the speaker, under the section labeled "Line In," being careful to match the channel on the CD player with the channel on the amplifier. Be sure that each jack is pushed all the way in. You will hear and feel a distinct click when this is done. Then turn the volume on the amplifier to a low setting.
Insert a CD into the CD player, set its volume to the same level as the amplifier and begin playback. If you turn up the CD, also turn up the amplifier a corresponding measure as well. Continue to do this until you have the ideal volume. Listen carefully for clicks, pops, hisses and other signs that the amplifier is being overdriven or underdriven. If you hear them, turn off the system and carefully check the converters and equipment for any loose connections or shorts.