How to create open world third person shooter game,How to create 3rd person open world game

I want to create 3 large island in my game.It will be open world zombie game.Two island would be completely ruined city.Please tell how to create such landscape in unreal.I Don’t have money to buy ‘world composition’.Please tell how create such open world terrain

A solution you could use would be:

1-Could possibly do it by making sure your landmass and water plugins are turned on.

2-Add ocean to your map

3- use the island tool to produce your islands

YouTube can show ya step by step I was playing around and found this out hope it helps