Jual,
First of all Welcome to the Forum.

Now you said that you will have Some Whites tree frogs, Well how many?
Have they been living together.
If they haven't been living together I wouldn't put them together until you quarantine them
separately.

Glad to hear that you have the terrarium, What size is it?

I wouldn't worry about substrate just yet,

Also you will need a heat source , light source , and a humidity source.

a water dish.

A source of feeders and a place to keep the feeders.

I hope you a ready LOL