Hello Mr. reptile,
I am no expert on White's Tree Frog, but I looked it up for you.
You can certainly put more than one Whites Tree Frog in the same tank as long as the sizes of the two frogs aren't too different. Otherwise you might risk the much larger frog mistaken the smaller frog for food.  Most frogs will eat anything they can swallow whole. Keep that in mind lol.
How big is your tank?
It is said that the minimal should be 10 gallon. Most sources recommend 20~30 gallon.
All the sources I have seen so far claim it is quite hard to sex white's tree frogs. One of the sources claims only the male frogs will croak and sing. Another source says the male frogs of at least one year old will develop "puffy little pads" near their thumbs and palms.
The best way to avoid getting baby frogs is to just have one.
A list of items from a checklist I saw -
1. Terrarium
2. Forest substrate
3. UV
4. Heat lamp
5. Timer (for automatically turn off the lights)
6. Thermometer
7. Hydrometer
8. Water Dish
9. Tree logs or branch for the frogs to climb on.
Source One
Source Two
Best luck to you. Please share some photos after you have everything set up. 
| 
