It looks like it might be an aftermarket job. That was my first impression when I saw it. Also, I didn't think the Capri had cruise control on a manual transmission.
Anyways, the controls are to the left of the steering wheel, in the padded part below the vents.
It is a four way switch. Up is on, Left is set, right is resume and down is off. When I turn it to ON the box glows orange, but it never sets.