Hello and welcome to Frog Forum.
Take your time and learn as much as possible first

build 1st
then buy the frog(s)
to mention a few: Josh's Frogs How-To Guides » Poison Dart Frog Caresheets
then quarantine the frog(s)
then the frog(s) can enjoy their new home

http://www.frogforum.net/section/vivarium-articles-114/

For the sake of saving time , here are a few additional good links:

How to set up a living vivarium for poison dart frogs

Josh's Frogs How-To Guides » Search Results » vivarium

New England Herpetoculture LLC - Vivarium Construction 101

the above retailers all sell supplies

ie....... Poison Dart Frog Vivarium Supplies | Josh's Frogs

How To Setup a Poison Dart Frog Terrarium or Vivarium - YouTube

Lynn