Pokémon FireRed and LeafGreen/One Island

Sevii Islands
'Welcome to Sevii Islands, where the next part of your journey takes place. You'll split your time among three islands, named One, Two, and Three Island. It's here that you'll have the opportunity to catch the famous Moltres. For now though, spend some time exploring.'



Arrival
When you first arrive, you'll be escorted by Bill to the local Pokemon Center, where you'll meet with Bill's friend, Celio, who's in charge of getting the local P.C. network up and running.

You'll be given a Tri-Pass, so you can ride the boat between the islands, a second page to your map that shows some of the Sevii Islands, and a Meteorite to give to a friend of Celio's, who resides in Two Island.

One Island
One Island is a small community, consisting of a Pokemon Net Center with a unique machine (one that lets you trade between Ruby, Sapphire, and Pokemon Coliseum, but you won't be able to use it for a while).

In addition, if you head left, you will see Treasure Beach, and if you Surf, you'll head towards Kindle Road. This is the way you must eventually follow to catch, but accessing its home will be impossible until you finish the quest Celio just gave you. Thus, it's best if you just head back to the ferry and set sail for Two Island.