Okay first you have to CATCH 60 Pokemon for your pokedex, then defeat the elite 4 & the champion, then go to 1 island, to talk to Celio(at the Pokemon center) talk to him, then go to Mount.Ember,
Notice, there are team rockets digging for something, they dug a cave, defeat them, then go inside the cave,
(you need strength & rock smash) go deeper & you will have an Item called "ruby", get it & give it to Celio, he will give you a rainbow pass, go to any island.
If you can, go to 6 island, (don't surf, go to the grass, then you will find a cave called "Dotted Hole",
Use cut on the door of the dotted hole, it will open, go deeply in the cave, there is an item called sapphire, then a professor will get the sapphire, he will give you the password to the Team Rocket warehouse in 5 island,
Go inside, pawn the grunts, & the professor who got the sapphire is there, battle him, & gives you the sapphire, go to 1 island, give it to celio & now, you can access the trade to emerald, sapphire, ruby, versions !