Operand 0 is the first operand in the instruction, which is the specification of where the Bit Array is stored.
This Array has to be a DINT array.
Operand 0 would most likely be the start of this array, e.g. DINT_Array[0], but could be located anywhere in the DINT array, e.g. DINT_Array[10]
Rather surprisingly, if the array starts at DINT element 0, the index [0] can be omitted, you can just enter DINT_Array for operand 0
If you are calculating the index, then remember it is not BIT NUMBER, but DINT WORDS NUMBER that should be in the square brackets. e.e. DINT_Array[MyIndex]
The error you get indicates that your index value is too large for the size of the array