1. Open the item, tap the pencil button (Edit), then Nutrition.
  2. Tap Look Up Nutrition Online.
  3. It searches for the item’s name. Change the words if you need to, then tap the matching food. A food that matches the item’s barcode is listed first, under Matches this item’s barcode.
  4. Go back and tap the checkmark (or Done) to save.

The item’s Serving Size screen has the same button. Choosing a food replaces the item’s serving size and nutrition. If the food’s values are per 100 g, you’re asked to choose what one serving is.

You don’t need an account to look up nutrition. The food database is online, so it needs an internet connection.