Congrats on the new disposal! And yay for responsive and responsible property management!

Yes, you need to run water when you turn on the disposal to grind up stuff. I'd put a heaping cup of material in there at a time, or thereabouts, not much more than that. Disposals apparently don't like fruit rinds/skins, stuff with hard seeds, bones, or tougher, think stuff. If you can find the make and model of the disposal on a label on the unit, you can do a Web search on it and maybe turn up a owner's manual or other manufacturer's recommendations.

Good luck!