Hi!

While you CAN put the frogs straight into the tank, a quarantine type setup is important to put the frogs in for at least 30 days.

A quarantine setup should include only the basics
-moist unprinted paper towels as substrate
-a water dish for soaking
-a place for the frogs to hide
-a few fake plants to climb on

It is important to monitor feeding and poop during this period.

Since you have three, i would not recommend letting their food run loose. Bowl feeding would be a good idea. But you should try to tong feed them so you know for sure exactly how much each frog is eating.

Remember to dust the food with vitamins and calcium and gut load them.

Generally, tree frogs do not swim well. Some individuals do seem to have a talent in the area of swimming though. I would recommend not having the water be deeper than the frogs chin. Also, i have found that adding a pond/water feature just ends up making a big mess. But if you are up to the challenge, go ahead.

In that size tank, even three is pushing it. I would not get another frog without getting a bigger tank.

Do you have confirmation from the seller that the frogs are all female? If not then there is a chance you will have a male among them.