General flow :
Set premise to false
While
Test premise
.......... change something
.......... test change
........................... set premise false or true based on change
But in your case, chances are that you dont need a 'while', if we speak about a 1 dimensional array.
Array > Contains value 'value'
................. in the actions the index of that value is stored in the expression Array.IndexOf('value')
Otherwise.
Local variable 'counter' ... number .. = 0
Local variable 'check' ... number .. = 0
While
'check' = 0
_______ Array .. Compare at XY ... x = counter .. y = say 1 ... compare to what you wanna compare
_______________Set 'check' to 1
_______System > Compare 2 values ... counter ... is the same as ... Array.widht - 1
_______________Set 'check' to 1
_______ System > Every tick
_______________add 1 to counter