You can’t make ice out of thin air—unless you’re a wizard, in which case, why are you reading this? You’ll need a cold water line nearby, usually under your kitchen sink.
Look for the cold water pipe—it’s the one that doesn’t make your hand feel like touching a ghost when you turn it on. If you see a hot water pipe, back away slowly; that’s the enemy of ice.
Once you’ve found it, clear out the clutter under there. I found a lost sock and three cat toys last time I did this. It’s an archaeological dig, but we’re focused.