That looks like a Frilly aka Slimey Sponge. They're awesome to have in a tank, it brings out so much color.
You don't have to do much, just put in your tank and place him in the substrate or in your LR. MAKE SURE the sponge NEVER hits open air. In other words, you take the bag he's in, fully submerge it, and then open it up and set him in. Usually it's a big no no to let any water from the bag to enter your tank but this is an exception.
Feeding? It doesn't need much, it filter feeds. You may want to consider adding a regular dose of Phytoplankton (the refridgerated kind, not the shelf stuff) once a week/bi-weekly. Also, try not to leave your light on too much, you don't want algae growing on the sponge.