Use File.Copy from System.IO. To access .NET static methods, right-click on the Toolbox and select Choose Items. When the dialog appears switch to the Pega Robotics Static Members tab. Select "From Global Assembly Cache" and then from the dropdown select "mscorlib, Version=184.108.40.206". From there you can select File and Copy.
From the Toolbox you can now use File.Copy in your automations.