Locate the RCA sockets on the Seeburg preamp. There will be two pairs, both with a red and white socket. Then locate another socket for the earthing cable and one for a stereo mini-jack.
Connect the tuner or other audio input, such as a microphone, to the preamp with RCA cables. Then connect them with an earthing cable, which is used as a thinner. This prevents hums and other unwanted noise.
Connect the preamp to the amplifier of the stereo, with another set of RCA cables. Connect a mini-jack into the appropriately sized socked in the Seeburg and the plugin that reads "line" on the stereo amp.
Test the sound quality of the audio system. It should produce a clearer sound than stereos that have the input, preamp and amp together inside a single receiver.