I am the only owner of an Alfa Romeo Spider Veloce 1991. I recently bought a factory boot cover, however, it comes with several brackets, metals and clips, which I don't know how to install them.
I was wondering someone may be able to help me.
Since nobody has chimed in yet, I don't have an S4, but I retrofitted an S4 top boot from Classic Alfa. That top boot cam with a whole bunch of plastic clips and metal brackets for attaching the clips to the boot. For the S4 boot, because it has the plastic "wings," you only need three of the plastic clips, which snap onto the silver trim piece just behind the folded top. The top boot I purchased had tiny slots cut in the underside of the boot through which the tines of one of the metal pieces pass. The image below (albeit not an S4 boot) shows how the plastic clips are installed.