At his house or at the vermillion city port.
He will appear after you beat the 7th gym leader.
Go into the Pokemon center on Cinnabar island and talk to bill (he's over on the right).
After you beat the Pokemon League, go back to the Pokemon Center in Cinnabar Island, talk to Bill, and he will take you to One Island and Celio gives you the Tri-Pass there.
U must go to Cinnabar Island and there u will meet Bill who takes u to island 1 to see his frend. His frend has u go on missions to do things for him and u will get to islands 2 and 3 by doing the favors. AKA, to get to Cinnabar Island, u need surf which u get in the safari zone if u find the secret house. u need to use surf in the little pond in pallet town where the fat guy in the white tshirt is standing. By surfing from that pond, it will take u to Cinnabar Island. : )
I've got it, and i forget how you get it, but i think that you get it from Celio or Bill. Anyways, did you beat Blaine yet? when you get out of the gym in Cinnabar, Bill will come to you with a boat and ask you if you want to go to One Island, because for Celio. Say yes!!
Either in his house (above cerulean city) or at the vermillion port.
he is gonna be at the Pokemon center in cinnabar island waiting for you to say yes
beat Blaine on cinnabar island with bill
go to cinnabar island and once you beat the Pokemon mansion Bill will come out and offer you to go with him to first island.
he will be in the Pokemon center in cinnabar island you can just talk to him.
To get the Tri Pass, you must progress in the game until you get to the Cinnabar Gym. After you beat it, when you leave the gym, Bill appears and talks to you. Then he will give you a Tri Pass and sends you to One Island to talk to Celio.
Beat Blaine on Cinnabar Island and Bill will take you to One, Two, and Three Island.
He will appear after you beat the 7th gym leader.
Go into the Pokemon center on Cinnabar island and talk to bill (he's over on the right).
You will need have beaten Blaine on Cinnabar Island to gain access to Island One. When you exit the Gym, Bill will ask a favour and take you to Island One.
When you defeat the gym on Cinnabar Island you will meet Bill outside. He will ferry you to Island One to meet Celio. Bill will then give you a Meteorite and the Tri-pass which will give you access to Island One, Two and Three.How_do_you_unlock_islands_after_beating_the_elite_four
The official name of island 4 on Pokemon FireRed is Floe Island. To access Floe Island you need the Tri-Pass from Bill. To obtain the Tri-Pass you need to have defeated the Gym Leader of Cinnabar Island.