Be careful with any web search for Iguana care sheets. You are sure to come across some care sheets that are notorious as being full of misinformation about Green Iguana care. You have already received some of what I consider to be less than optimal, albeit controversial, information about diet right here in this thread regarding feeding of kale to a green iguana.
In my opinion, Kale should not be a diet mainstay or even a large part of the diet, but is acceptable in small amounts in the diet. Kale is reportedly akin to spinach in that it contains oxalic acid and can interfere with absorption of calcium a necessary mineral in iguana nutrition. Sure Kale also contains calcium but the OA interferes with its absorption making kale a poor choice in my opinion. Like spinach, kale should be fed only as part of a vegetable diet high in leafy green vegetables, and even then only in small amounts. It is also my understanding that fruit should comprise a small portion of a Green Iguana's diet - say about 5 to 10 percent so be careful not to overfeed fruits to it. As to good greens to feed to a green Iguana, my opinion is that you would be better with: clean pesticide and weed killer free Dandelion Greens, Turnip Greens, Mustard Greens, Maple Tree Leaves (regular maple trees such as sugar maple, not Japanese Maple), Parsley, Escarole, Red Leaf Lettuce, Green Leaf Lettuce for up to 50 percent of the diet, to be followed by other vegetables about 40% such as green beans, shredded carrots, chopped squash, corn (kernels), followed by fruits (10%) such as strawberries, raspberries, blackberries, blueberries, chopped apple.
I am not looking to argue with anyone here, just to discuss the issues while trying to point out that you will get lots of information and opinions about the proper diet for a green iguana - much of which will be in disagreement with what you already may have found. What I suggest is you go with the care as suggested by reputable breeders, or zoological establishments. While they may not all agree on every aspect either, I think you will find they have lots more experience which they express in their care sheets than many others who post care sheets on the web, and you will likely learn they are more likely to have the better information.
I am of course assuming, as others apparently have, that you mean you found a Green Iguana and not something like a Desert Iguana or Rhinoceros Iguana. If you are not very familiar with Iguanas then also make sure you did not find a Water Dragon, many of which resemble iguanas. Make sure of what you have before you try to figure out how to care for it.
All the best, and good luck,
Glenn B