While in the design editor, hold down the Shift key on a keyboard.

Still holding Shift, select each text box that needs to be aligned.

Select Position from the top toolbar and then select an alignment option from the dropdown menu.

This can also be used to align graphics with text boxes. Make sure to choose only the items that need to be aligned. If a graphic is aligned by accident, use the Undo button on the right side to go back to the previous version.

For more visual guidance, please watch this short video demonstrating the process:

See also: How to Align Elements.