In the Task Pane, select the Design
Library tab 
.
Click Add File
Location 
.
In the Choose Folder dialog box, browse to a folder, then click OK.
Add an existing folder to the Design Library tab in the Task Pane. This procedure is a shortcut to specifying a Design Library folder in Tools, Options, System Options, File Locations. See also Add Existing Folder.
To add a file location:
In the Task Pane, select the Design
Library tab .
Click Add File
Location .
In the Choose Folder dialog box, browse to a folder, then click OK.
You can select Show
assemblies only to filter the files when you browse.
The folder appears at the top level (the same level as the Design Library, Toolbox, and 3D ContentCentral folders) in the upper pane and is referenced for Design Library in Tools, Options, System Options, File Locations.
If you delete a folder that
was added using this procedure, the folder remains on disk. Only the reference
in Tools, Options,
System Options, File
Locations is removed.