You can align either layers or the contents of layers and layer sets using the Move tool. (See Moving selections and layers within an image.) In ImageReady, you can align layer groups.
To align the contents of layers:
Do one of the following:
To align the content of a layer to a selection border, make a selection in the image. Then select a layer in the Layers palette.
To align the contents of multiple layers to a selection border, make a selection in the image. Then link the layers you want to align in the Layers palette. (See Linking layers.)
To align the contents of layers to the content of the active layer, link the layers you want to align to the active layer. (See Linking layers.)
To align multiple layers (ImageReady), either select multiple layers with the Move tool or select a layer group.
Choose Layer > Align Linked or Layer > Align To Selection (Photoshop) or choose Edit > Align Layers (ImageReady), and choose a command from the submenu. These same commands are available as Alignment buttons in the Move tool options bar:
Top Edges aligns the top pixel on the linked layers to the top pixel on the active layer or the top edge of the selection border.
Vertical Centers aligns the vertical center pixel on the linked layers to the vertical center pixel on the active layer or the vertical center of the selection border.
Bottom Edges aligns the bottom pixel on the linked layers to the bottom pixel on the active layer or the bottom edge of the selection border.
Left Edges aligns the left pixel on the linked layers to the left pixel on the active layer or the left edge of the selection border.
Horizontal Centers aligns the horizontal center pixel on the linked layers to the horizontal center pixel on the active layer or the horizontal center of the selection border.
Right Edges aligns the right pixel on the linked layers to the right pixel on the active layer or the right edge of the selection border.