Basically you water most plants when the compost has dried but before it becomes parched. If the pot is standing in another container water will drain through into it. This is a tropical plant and does like its roots in water so err on the damp side rather than the dry and it should enjoy there being some residual water in the bigger pot.
The pot yours is in looks on the small side and it might be a good idea to give it a bigger one. Be prepared for a happy plant to grow quite tall. Try Googling it as you'll find more complete instructions there.

There is no formulaic answer for how much water a plant needs - it varies depending on the season and the temperature, but this is an easy care houseplant, I've had one, or offspring from the original, for years. Can be grown up a moss stick or left to trail, with no support.

As with the majority of houseplants, never leave it in standing water (sorry, Steragram), water liberally during spring and summer, and sparingly in winter. Water when the surface of the compost is dry to the touch, but not shrunken from the sides of the pot (parched, as Steragram describes it), and water thoroughly when you do. If there's any water left in whatever it stands in (tray or outer pot) 30 minutes later, empty it out. Under normal home conditions, you can expect to water it well around once a week, but that's only a guide.

They don't like direct sunlight in summer particularly, but do need bright light to retain variegation - an east or north facing window is fine. Keep away from heat sources such as your tv or a radiator, and draughts, which they particularly don't like. Minimum temperature, 10-15 deg C. You can feed with something like Baby Bio during spring and early summer.

You'll probably find it produces aerial roots as it ages - these should be tucked into what I hope is a moss pole up the centre of the plant in your picture.

Cuttings root easily in water.