So the kit came with the two H4 adaptors, wirings and a ballast right? I've installed a kit on my cousins Celica and its fairly easy. You need to take off the headlight, mount the ballast and install the H4 adaptors where your regular bulbs usually go.
The only problem is that he has two bulbs and we have one on our Focus. This means you will no longer have functional high-beams.
Did it come with a wire harness. If not you can get one from a VW dealership or the Ford dealership. They use to be like $30 for both but Ford hacked up the price now and I think it's $40 for EACH ONE.
Here is a very good website on instructions with pictures and step by step.