An Array is a series of variable elements each with an identical datatype and data source.

In the example below an integer type Variable was created.
By changing the ArrayDimension from 0 to 2 the variable will now have components nested under the variable name.

In this example the Source was changed to PLC and a 4X register address was assigned to the variable components by right clicking on the variable and going to Configure Device Address.
Left clicking on the components of the variable with the inspector window open will show the assigned register address for each component and its individual configuration options.