CC Libraries are different than CS6 libraries.
CC libraries can contain many things - essentially anything that can traditional be saved externally - swatches, object styles, cell styles, table styles, etc. CC combined all externally savable items into one common location.
CS6 Libraries merely contain saved objects. With CS6 you create an object and then add ...
Select the Move Tool.
Select the layer you want to center.
Press Ctrl / Cmd + A to select all. (This creates a selection the size of the canvas which you can then align the selected layer according to.)
Use the Align vertical centers and Align horizontal centers buttons in the top tool bar or use Layer > Align Layers to Selection > Vertical Centers and ...