you can also use 2 bosch relays, 1 for up and the other for down, and use a 2way rocker switch to control the ground on the relays. but fusing the power to the relays would be a good idea. If this is a 2 wire motor the relays would better, because when 1 relay applies power, the other applies ground, and the other way around.
It's a pretty pink color on this radio but many of the connectors did not even have a wire in this spot. Yours may be blank. On the earlier 5th gen Elkys it may be a yellow wire but it's the same connection point.
Remember, this is not to power the antenna motor. It's only to energize the antenna relay!
The 12 volt antenna output from the radio energizes the coil of the antenna relay (which is usually a part of the power antenna). The contacts of the antenna relay then switch a fused 12 volts to the antenna motor. The motor draws a lot of current so the 12 volts to drive it has to have a separate feed from the fusebox.
The pink wire is the "ANT" output from the radio and is fused for 10 amps. The orange wire is the power for the antenna motor and it's fused for 20 amps. Even though the schematic is for a 3rd gen Camaro it's identical to the El Camino.