Ponytails are easy indoors or out. They don't need a lot of water, so allow the pot to dry out significantly before rewatering. They enjoy good light indoors, so near a window is ideal. When it gets too tall, cut it in half and plant the top half. The bottom will (probably) sprout two new heads. Remember, it's a palm, so nitrogen fertilizers are good in spring and summer, phosphates in autumn.

I don't know where you bought it, but you should probably check to see whether or not it has a layer of glued-on pebbles. Some stores insist on putting these on, but they will most likely lead to the roots rotting if they are left on.
-Jmcat