Go to the dock and talk to the guy inside and he'll ask you where you want to sail.
i think there are only 3 islands Acually there are 7 islands
In the Valcano on one of the 3 islands.
Go to vermilion city and go to the harbor show the sailor your tri pass to go to islands 1-3.
You need to catch more than 60 Pokemon and talk to Oak and get the National Pokedex from him and then go to Island One and talk to the guy near that big weird machine and he'll exchange your tripass for his rainbow pass which allows you to travel to the Sevii Islands (islands 4 - 7) and the first 3 islands.
There are 7 catchable rare Pokemon in leafgreen however here's the catch, there are 7 but you can only catch one of 3 legendary dogs Raikou/Suicune/Entei it depends on what starter Pokemon you chose. Also there are 3 event only Pokemon you can get making the total to actually 10 in all.
i think there are only 3 islands Acually there are 7 islands
In the Valcano on one of the 3 islands.
loreni is in the back of berry forest on island 3
Fly To island one and use surf
when you talk to bill you can go to islands 1 2 and 3 on the same ship
Go to vermilion city and go to the harbor show the sailor your tri pass to go to islands 1-3.
moltres mt.ember articuno seafoam islands zapdos power plant south of rock tunnel
Articuno: Seafoam Islands Zapdos: Power Plant Moltres: Mt. Ember
You go there by defeating Blaine in Cinabar Island after you go out Bill Will be there waiting for you to go to Islands 1,2 and 3. Good Luck
island 3
Venusaur
There is no Mew 3.