The vital parts are cable stops where the housing for the cable ends and the cable proceeds down in the midline of the bike to the brake. The short cross cable that links the brake arms is attached to the brake cable by a delta shaped metal bit. The cable stops are typically attached 1)to the head set somewhere (top usually) and thus rotates with the front wheel. It is a metal ring large enough to fit over the threads in the headset with a tang bent down that has a cable stop at the bottom. 2) In the rear a metal V with two circles
large enough to be mounted on the seat tube seat clamp bolt (one under the bolt head, one under the nut) with a cable stop at the bottom of the V pointing down toward the brake. If these didn't come with the brakes you will
have to find some. Old established bike shops may well have them in the back somewhere covered with dust.

Barnetts Manual Chap 35/36 has a few pix: 35.11 for side view of rear cable stop. Pix 36.32 or 36 for the cable attachment to the short cable between the brake arms. Steve