To Copy Standard Content to a Custom Content Library (AutoCAD Mechanical Toolset)

Click Content tabLibrary panelContent Manager. Find
In the Content panel of the Content Manager dialog box, select the destination library.
In the Content panel, select the Standard Content to copy.
Right-mouse click and select COPY from the context menu.
Select the destination location under the Custom Content node. Right-mouse click and select PASTE from the context menu.
The selected content and all its views are copied from Standard Content to the custom library.