White's tree frogs in the wild spend most of their time in trees, and need an enclosure with lots of climbing room. A minimum 25 gallon aquarium is recommended, and the arboreal type (tall rather than wide, often hexagonal) is better. A tight fitting lid is essential, as these frogs have foot pads that will let them easily scale the side of any aquarium. More than one can be kept in a tank, as long as they are of similar size (otherwise the larger ones may eat the smaller ones).
Larger pieces of bark, large sized gravel, or soil can be used, and can be covered with sphagnum moss (which will help retain moisture for humidity). Avoid small sized gravel or bark or the frogs may accidentally ingest it. Some keepers prefer a more bare approach, simply lining the tank with paper or paper towels to facilitate cleaning (it is a bit harder to maintain the appropraite humidity this way, though).
Provide lots of branches, large pieces of cork bark, and foliage for climbing - keeping in mind that it needs to be quite sturdy to support these stocky frogs. Live plants can be used, although they must also be sturdy and they must be free of fertilizer or pesticide residues (on the plant or in the soil). Live plants in the terrarium can be kept in small pots to make cleaining the tank easier.
Placing a large piece of bark diagonally across the cage, a couple of inches from the back wall will allow the frog to hang from the back of the tank under the cover of the bark to sleep during the day. Alternately, any sort of thick plant cover or hide that allow the frog to hide during daylight hours can be used. Covering the back surface of the tank with dark paper will help the frog find a secluded and dim area to sleep during the day.
A piece of paper a couple of inches tall placed around the bottom of the tank may help if the frog tends to rub its nose along the glass to try and "escape."
Temperature and Lighting
Because these frogs are nocturnal, there are no special lighting requirements (i.e. exposure to UVB is not necessary, although some exposure won't hurt). However, a basking light or heater should be provided, outside of the cage, to provide a gradient of 80-86 F (27-30 C) during the day, with a drop to 72-78 F (22-25 C) at night. As always, use a thermometer to confirm that appropriate temperatures are provided. Lighting should be subdued (and if needed at night, use a nocturnal bulb), and a regular light-dark cycle should be used (12 hours light and 12 hours dark should be acceptable).
Humidity should be maintained at about 50-60% The tank should be misted daily with dechlorinated or bottled (not distilled) water. A dish of water should also be provided. Frogs like to get into water to rehydrate and soak, so it should be large enough that the frog can comfortable sit in the dish, but not too deep that there is a risk of drowning (tree frogs are not strong swimmers). Do not use fresh tap water with frogs and other amphibians, due to the chlorine used in the water purification process. Water provided in the dish and used for misting should be allowed to sit in an open container at room temperature for 24-48 hours ("stale" water), and ideally treated with a dechlorination kit available at pet stores. Alternatively, bottled water can be used, but do not use distilled water.
Cleaning and Maintenance
Your frog's cage should probably be spot cleaned every day, wiping off any large bits of waste matter from the plants and bottom of the tank. The water in the dish should be changed daily or at least every other day. If paper is used to line the cage, this can be changed often. If bark or moss is used, it can be taken out an washed as needed - the more often the better. Soil should be changed as needed. Plain hot water is the best choice for cleaning - with soaps or disinfectants there is a chance of leaving residues which could be absorbed through the skin and harm the frog. If disinfection is necessary, rinse very well and dry thoroughly. Replace any water with stale, dechlorinated water.