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Hi,

You can create special folder for your custom CTB files somewhere inside your Home folder, put your CTB files there, than add the path to this folder in AutoCAD preferences:

Or put custom CTB files to the "/Users/YOUR_USER_NAME/Library/Application Support/Autodesk/roaming/AutoCAD 2015/R20.0/enu/Plotters/Plot Styles/"

Maxim