ahhh, you don't have a signal setup! well, the tech is right, you need to use the xtra wire that's brake only to hook up your brake lights for now - when you have a signal system in, the wire from the brake light switch will go to the column unit, then on to the brake lights from there - as I said, when you signal, the flasher uses the brake filament, interrupting it if the brakes are on at the same time
at the rear, there will be one wire for tail/license lights, hook'er up - then there's one for right brake[turn], one for left brake[turn], those 2 will be inop until you get the signal setup happening, so for now the extra wire for 3rd brake light does both brake lights [or all 3], later only a 3rd light if you have one
Bill