That kind of brace installs to the front LCA bolts. You remove* them, put the bolt thru the cup, and then put the bolt back where it came.
FWIW, this style of bracing already exists on the Capri, in the form of two small struts/rods that bolt to the engine subframe. This piece will be stiffer, but may reduce your ground clearance.
*The LCA bolts are a colossal pain in the ass to remove. They're retained by a square nut hidden up inside the frame. The nut is held in place by a flimsy piece of sheet metal. Most rust a bit, and when you turn the bolt, it spins the nut, and bends the sheet metal piece out of the way, permitting it to just spin endlessly. They were designed only to be assembled at the factory, not with service in mind.
I have stuck my welder in there to put a piece of snot on the nut to keep it from spinning, this has had mediocre results.
I have seen capris where the frame has been cut back/peeled back to access the bolts. This allows you to jam something in there to pin in between the wall and the nut. I have done this, and re-welded the pieces back into place. This is a much more invasive, but reliable method.
It will be worth your time to replace the LCA bushings with urethane ones while you're in there. There is a thread here with part #s.
You don't want to do this job twice.