If you have multiple layers and you need to align the content of the layers (left, right or center aligned), you can select those layers in the Layers panel and then, with the Move tool selected, choose the desired alignment option.
In the illustration on the left, all of the circles are on different layers and all of the layers are selected. Then, with the move tool selected, the Align center option was chosen in the Options bar. The circles are aligned based on their locations.
If you want to align the layers to a specific location, use the marquee to select that location and then choose the alignment option.
When a selection is made in the image (the dotted line in the image) and the align option is selected, the circles are aligned to the selection.