Are you talking about pokemon emerald or ruby. To get groudon as a shiny, you will have to save in front of it . Groundon battle it . If it is not a shiny groundon soft reset and try again. It can take days because there is only one groudon and the chance of getting a shiny pokemon is 1/ 8,192. Unless you cheat using an action replay.now were to find him he is in a cave called the terra cave. Terra cave is a cave found by the shore after defeating the elite four. It is on 105, 127, 125 or 129. You will need to go to the weather center and he will tell you were it is. If you take too long finding it it will move on. Its a basic cave first groundon the misty cave. In the misty cave you will see groudon. Go and battle him . Make sure you save.
