If you mean Pokémon Fire Red, then you get the National Dex, which enables you to trade Pokémon from Generation III over from Ruby, Sapphire, and Emerald. Also, Cerulean Cave's guard will vanish, enabling you to enter Mewtwo's home. But if you mean the original Red Version, then there's no answer; Celio and the Sevii Islands did not exist except in the Generation I remakes, Fire Red Version and Leaf Green Version.
Give it to celio in 1 island
In sapphire you need to beat the elite 4 and in fire red you must give Celio his ruby and his sapphire. if that is already done and still no luck then i can't help you.
You find the ruby and give it to celio
you can, the person with the fire red or leaf green needs to win the game then get the ruby and sapphire and give them to the professor that is building the machine to trade with ruby and sapphire games on island one
the Sapphire and ruby plates in leaf green are two plates that you have to give to celio to be able to find one of the three legendary dogs.
You give it to Celio
You go to one island and give them to celio in the pokecenter.
You also find the sapphire and give them both to Celio.
Give it to celio in 1 island
fire red: after you give the sapphire to celio, now you can trade with Pokemon ruby, sapphire and emerald
Give it to Celio on One Island. You also need the Ruby. Once you give both to him you will be able to trade Pokemon with Ruby/Sapphire games
You get the Sapphire in ruin valley and give it to celio.
give it to celio and then mewtwos cave will be unlocked
You cant have the ruby and sapphire at the same time because you have to give the ruby to celio in order to get islands 4-7 which is were you get the sapphire
The elite four will open and they will be stronger and you can now trade with ruby, sapphire and emerald.
Yes if you give Celio the ruby and sapphire he connects with Lanette and all Hoenn trainers this means you can now trade between ruby, sapphire and emerald and even Pokemon colosseum and Pokemon xd gale of darkness.
The sapphire and Ruby (you can find both in the game) allows you to trade with Pokemon ruby, sapphire and Emerald version give it to Celio and when you give both to him it will allow him to connect with the Hoenn region allowing you to trade with those versions