Basiccly, if you doesn't had any island (or just started) you can do by making an island by typing /island create on the chat. If you wanna go back to your island, you can do or type /is go also like TeKkaTi says, which is you do /is go but you keep teleported to island, you can do /settings and than turn of the safety teleportation, but please note turning off safety teleportation is dangerous and if you doesn't need to turn it off again, you can consider to be just turn on the safety teleportation.