How do I set an object's frame dependent on an instance variable and array?

What I want to do is have an icon be set to a check or x dependent on if the instance variable it has is inside of an array.

How do I do this?

the instance variable it has is inside of an array

I don't know what you mean by that.

To set animation frame to an instance variable you can use this action:

Sprite set frame to self.Var

To set animation frame to a value from an array:

Sprite set frame to Array.At(index)

I want to detect if the instance variable is inside of an array.

Then set a frame dependant on if it's there or not.

You can use Array.indexOf(value) expression. If Array.indexOf(value)<0, this means the value was not found in the array. For example:

System Compare Two Values: Array.indexOf(Sprite.var)<0
... Sprite set animation frame 0
Else 
... Sprite set animation frame 1