To select multiple elements:
Hold down the Shift key, and use your mouse to select the desired elements on the stage or from the Layers panel. Each element that is selected displays a 2 pixel blue border to indicate that it has been selected, and is highlighted on the Layers panel.
To deselect a single element when multiple elements are selected:
Hold down the Control key (Command for Mac) and click the desired element either on the stage or Layers panel. If a locked layer is selected as part of the group and any of the actions are attempted, the locked element will not be affected. Unlock the element first, if you wish to perform an action on that element.
Tip: When dragging an element on the stage, hold Control (Command on Mac) to lock the X coordinate to constrain movement vertically, and Shift to lock the Y coordinate to constrain movement horizontally.