To move items in Build an Island on Roblox, open the build or edit mode, select the item you want to move, and use the move/drag option to place it somewhere else. If the game treats some objects like placed structures, you may need to remove and rebuild them instead of moving them directly.

What usually works

  • Enter build mode.
  • Click or tap the item you want to reposition.
  • Look for a move, drag, or edit control.
  • Place it in the new spot and confirm.

If it will not move

  • Make sure the item is not currently in use.
  • Check that the target space is clear.
  • Try rotating it first if the game only allows placement changes.
  • For some games, fixed pieces cannot be moved and must be broken down and rebuilt.

Small note

I could not verify a game-specific official guide for this exact Roblox experience from the available sources, so the steps above are the most likely in-game method based on similar island-building games and general Build Island info.

TL;DR: Go into build/edit mode, select the item, and use the move/drag option; if it is a fixed structure, you may need to delete and rebuild it.