The variable values come from a CSV file.
The way to do it depends on your script configuration. But let say your CSV file is configured with the change policy "For each virtual user". With that configuration, the same value will always be used by your virtual user between each loop iteration.
To configure NeoLoad to use a different value on each loop iteration, you can insert the "Variable modifier" logical actions at the end of your loop.
Then in the Variable modifier configuration, in the "predefined variable" field, indicate the name of your CSV variable.
Select the option "Modify value". That's it.
On each loop iteration, NeoLoad will use a new row from your CSV file.
For more information you should check the NeoLoad documentation: Variable Modifier