Change the stack order of layers and groups

Do one of the following:

Drag the layer or group up or down in the Layers panel. Release the mouse button when the highlighted line appears where you want to place the layer or group.
To move a layer into a group, drag a layer to the group folder . If the group is closed, the layer is placed at the bottom of the group.

Note: If a group is expanded so that you can see all the layers within it, adding a layer beneath the expanded group automatically adds the layer to that group. To avoid this, collapse the group before adding the new layer.
Select a layer or group, choose Layer > Arrange, and choose a command from the submenu. If the selected item is in a group, the command applies to the stacking order within the group. If the selected item is not in a group, the command applies to the stacking order within the Layers panel.
To reverse the order of selected layers, choose Layer > Arrange > Reverse. These options appear dimmed if you do not have at least two layers selected.

Note: By definition, the background layer is always at the bottom of the stacking order. Therefore, the Send To Back command places the selected item directly above the background layer.