To change input voltage, and it is a multitap ballast. All you need to do is open the ballast compartment and look for the wires that you normally hook the power too. You should see a wire labeled "com" and possibly other wires labeled 120,208,240,277 and maybe 480. You want the "com" (neutral), and the 120 (hot). The rest should be pre-wired in that fixture.
To test a ballast you need to look at the sticker on it and find where it says "OCV" open circuit voltage, sometimes ov , cv or oc. Using a voltmeter put the leads on the bulb socket inner threaded ring and the tab that contacts the end of the bulb. You should get a voltage reading of the OCV +/- 5%.