Tap Add Item, give it a Name, a Quantity and a Category.
Tick items off as you pack them. The count at the top shows how many are packed.
Categories are Accessories, Beach, Clothing, Documents, Essentials, Flights, Footwear, Health, Hotels, Kids, Outdoors, Stops, Snacks, Tech, Toiletries, Work and Other.
Everyone you share the itinerary with sees the same list, so you can split the packing.