Plant it in a 50% sphagnum peat/perlite mix, place in bright shade & keep moist. Secure the cutting so it cannot move in relation to the container - this hastens establishment of the cutting as it eliminates breakage of fine adventitious roots as they form. Here's a post I left on another forum about rooting in water:

Though roots form readily and often seemingly more quickly on many plants propagated in water, the roots produced are quite different from those produced in a soil-like or highly aerated medium (perlite - vermiculite - seed starting mix, e.g.). Physiologically, you will find these roots to be much more brittle than normal roots due to a much higher % of aerenchyma (a tissue with a greater percentage of inter-cellular air spaces than normal parenchyma). If you want to eventually plant your rooted cuttings in soil, it is probably not best to root them in water because of the frequent difficulty in transplanting them to soil. The "water roots" often break during transplant & those that don't break are very poor at water absorption and often die. The effect is equivalent to starting the cutting process over again.
If you do a side by side comparison of cuttings rooted in water & cuttings rooted in soil, the cuttings in soil will always (for an extremely high % of plants) have a leg up in development on those moved from water to a soil medium for the reasons outlined above.

Al