Well, start with good power cord attached to 3 pronged timer. You'll probably want to hang the fixture with some chain to make it moveable. Does the ballast have a 3 prong cord or is straight-wired? Do you have a reflector? You're going to need all the light you can muster with 100 watts. You may even consider supplementing with some CFLs.
I'm assuming the ballast already has the mogul base (screw in) attached/mounted? Verify the ballast is HPS and not Metal Halide.
Check out the GrowFAQ at top of page. You'll likely need more than the items you've listed.