ask your dad why you need to use salt, and no do not use instant ocean whatever you do!!! Instant ocean is for "saltwater" aquariums, not "freshwater" aquariums. Matt remember this before you tell other people.
I am of course referring to aquarium salt. You'll see it in cartons in the pet stores labelled Aquarium Salt. You certainly don't need Instant Ocean. While I'm not sure on the harm it would cause if added to a freshwater tank, if any, there's no reason to pay the extra money for it. Standard issue aquarium salt.