Use the Align tool to center an object on the artboard in Adobe Illustrator CC or to align objects to other, specific objects.
Center Objects on the Artboard
Open a project or create a new file and place the object you want to align on the artboard. Select the Selection Tool from the toolbox -- or press V -- and then click on the object to select it.
Click Window and select Align from the menu to display the Align dialog. Alternatively, press Shift-F7 to display the dialog.
Click the Options button -- it has four horizontal lines -- and select Show Options to display additional options at the bottom of the Align dialog.
Click the Align To button and select Align to Artboard to align the object to the artboard.
Click the Horizontal Align Center and Vertical Align Center buttons to center the object on the artboard.
Align to Another Object
Select both objects using the Selection Tool. Hold Shift and click each object to select several objects. Open the Align dialog and display the Options section.
Click Align To and select Align to Key Object.
Click the key object you want to align to and then click the Horizontal Align Center and Vertical Align Center buttons to center the other object over or beneath the key object.
Press Ctrl-S to save the project. Save your work periodically to avoid losing it in case Illustrator crashes or freezes.