To create a rectangular array from one or more objects first select them.
Next click the Edit→Array→ button. This dialog box shown below will appear.
Rows and Columns
Enter the number of rows for the array.
Enter the number of columns for the array.
Enter the row (vertical) spacing.
Enter the column (horizontal) spacing.
Click the button to create the array.
Click the button to interactively create the array. As you drag the mouse in the viewport the array of objects will dynamically re-size according to the position of the mouse. Click the left mouse button to finalize the placement of the objects being arrayed.
Remember, you can always click the button to undo a change. This lets you easily experiment.