Lots of water, Impatiens can actually "live" in a glass of water. They don't like too much sun and you must water often. One of the few plants you really can't overwater. Pinch them back as they grow to make them fuller and keep them from getting long and leggy by end of summer, pinch and poke them to make new plants see message on subject below in this forum. They are one of the easiest plants to grow and maintain and propagate. Water is the key, they don't need much else, a bi-weekly addition of water soluable fertilizer doesn't hurt either.
Pauline

Lisa- you can add your mulch any time. You'll probably want to water the hanging baskets more often than those planted directly in the ground, as baskets/pots dry up more quickly. Up until mid-July I usually feed them half strength Miracle Gro, and then back completely off. As Pauline said- they do love water and probably the only danger is letting them dry out- hard to revive them if they've been left too long in a dry condition. During really hot weather I might water mine twice in one day. You picked a wonderful flower for your first try at growing them!
-Nan

Impatiens are absolutely GREAT plants, you will LOVE THEM! Follow the advice already given and learn how to take cuttings later on in the summer/early fall so you can grow them in a sunny window all winter too! Easy as can be to grow and so many different colors as well as DOUBLE flowered that look like small roses!

Welcome to the FUN!

Tom