you need to go to mount ember and move team rocket to move out of the way somehow
it is in a cave
find the ruby and give it to celio.
You find the ruby and give it to celio
beat the elite four
You also find the sapphire and give them both to Celio.
Nothing to do in Ruby. Just find a ruby and a sapphire in leafgreen or firered and give them to Celio.
Find the Ruby inside Mt ember and then give it to Celio.
When you beat the elite 4 and find the ruby and Sapphire for Celio!
You can do this after you find the Ruby and the Sapphire for Celio in Pokemon FireRed. then you can trade with Ruby, Sapphire and Emerald.
After getting the ruby from mt ember after beating the elite four, give the ruby to celio and he will give you the rainbow pass.
give it to celio
After agreeing to find the Ruby for Celio, head north to Mt. Ember. You will find a cave where two Rocket Grunts are standing. Battle both of them and then explore the cave. You'll find the Ruby in the final room; once you have it, take it back to Celio, and he will ask you to find a Sapphire to go with it. Then he will give you the Rainbow Pass so that you can find it.