Welcome to BYC!
Congrats on your first ducklings! Basics, For feed you'll want to provide either an All Flock/Raiser Feed or a feed specifically formulated for ducklings, you can also use a chick starter feed, but it's important to add a supplemental source of niacin to help prevent leg problems, that could be in the form of Brewer's yeast, nutritional yeast, B complex or a poultry vitamin. For water, they should have a container they can easily clean their nares out with, but avoid big containers till they are older since ducklings don't have waterproof feathers and can get chilled easily or possibly drown.
If you start offering treats you'll also want to provide chick grit on the side as well, just in a small dish, they'll eat it as need be. For bedding avoid Cedar, Newspaper, Cardboard or paper towels. Cedar can be toxic in unventilated areas and the rest are slippery and may cause spraddled legs.
They can be taken out for little trips outside, just watch them and see if they start to shiver, huddle together or look lethargic. It depends on your climate, but a good guideline to go by is they can be let out permanently once they have all their adult feathers in.
Best of luck with your ducklings! Enjoy them while there still small.
Treats for ducks-
https://www.backyardchickens.com/threads/the-ultimate-list-of-duck-treats-and-supplements.242460/