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As the instructions say it gets connected to ignition "on" (switched) power.
Since radios are so often replaced and rewired it's hard to know what you have but any* yellow factory wire near the radio is switched power. It should only have +12V when the ignition switch is in the "run" position.
*note there may be a yellow wire running from the radio area back into the center console. This is the power antenna trigger wire. If it's properly connected to the radio you can use it as it only goes hot when the radio is actually turned on.