At the moment there are a couple of bugs in this version, that are already fixed in the new one, but if you follow these steps, you can do it.
1-Buy a knife in the tool shop, or you can also get one, in the mission of rescuing the kidnapped people, (check the bodies of the dead kidnappers).
2-Make sure you have enough food or drinks to help you regain some life.
3-Fast travel to Elizabeth's house on island one. Then go all the way to the right, until you see the end of the island and a cave entrance covered with weeds. (Here's a bug if you don't have the knife in your inventory).
4-Once in the cave there is a box that you have to move, to be able to go up to the next level, move the box before interacting with anything else, you have to take it, to where you can see a broken rope ladder. (here is the second bug, but if you put the box first it's ok.
5-After that, comes the "EASY" part hahahaha, in another of the caves, you will have to guess how to pass through a ground that breaks if you don't follow the safe path, (tip look of slightly high and lower ground and turn according to the case) It could take a few tries. In other caves there are animals that will do you a lot of damage if you are not quick and careful at the time of passing, I have done it without receiving any damage, and other times I have died in the attempt. So I suggest you save before you try.
If all this seems too much to you, I recommend you to wait for a next update, since that content is still in process.