The operator
&&
(spoken: 'AndAlso') is used to logically combine its left expression with its right expression and requires both these expressions (Array[0] and Array[1] in your case) to evaluate to the type of boolean. But your array 'Array' is an array of strings and accessing an index (like Array[0]) evaluates to the type of string.
You did it right with the third expression: Array[2] == Array[currentPlayer] , it evaluates to boolean because you use == to compare two strings. You need to replace Array[0] and Array[1] also by expressions that evaluate to boolean. Probably like this:
if (Array[0] == Array[currentPlayer] &&
Array[1] == Array[currentPlayer] &&
Array[2] == Array[currentPlayer])
{