Your best bet is to go to a book store or library and get some books on frogs.
I got stuck with an African Clawed frog and really didn't know anything about them. When I attempted to put some Cories in the tank, he thought they were lunch! I saved my fish, but it was close. They will eat anything that will fit in their mouths! He now lives in a 30 gallon all by himself (waste of a tank, imo). I don't recommend ACFs, they get fairly big and can live 25 years. They are also messy and require diligent tank maintenance.
Many people love African Dwarf frogs. If you choose an aquatic frog, you need to get some beginner's books on aquarium keeping, their needs are similar to keeping fish. You should plan on at least a 10 gallon tank. That is usually adequate for a frog. You will use room-temperature tap water to which you have added a conditioner/chlorine remover (such as Aqua Safe or Start Right), you will need a tank outfitted with hood, filter, and I believe a heater. ADFs are very small and peaceful, they can be successfully kept in a tank with fish.
That is all I know on the subject. Read some books on them to know what species there are, what to expect and what you are getting into. Good luck!
Hobbyist for many years.