So all I did was move the thing where you were checking if the player one position had a ladder to right after the first user rolls their dice. It was dectecting the ladder cause you weren't doing
[currPos1-1]
in
(board[currPos1].contains("Ladder"))
so I had to change it to
(board[currPos1-1].contains("Ladder"))
since the index of an array is starts from 0 not 1.

I did that with the other if and else for player 2 as well.

I also added this extra piece of code to allow the snake thing to work
if(board[currPos1-1].contains("Ladder"))
    {
      currPos1 = ladder(currPos1);
    }
    else if (board[currPos1-1].contains("Snake"))
    {
      currPos1 = snake(currPos1);
    }
exact same thing you were doing with the ladder but now you're checking if it contains a ladder

Again added that to player 2 as well.

Here I removed the if statement in the ladder method you had at the end and just changed it to this, it wasn't needed.
System.out.println("You landed on a ladder and your positin is"+currPos+".");
  return currPos;

All you need to do is just add a print that tells the user in the snake method that they landed on a snake and just clean up the prints.