Steps to create your environment:

• Add necessary files:  if you intend to use predefined sisNET Named Expression, copy the SISNET_NAMED_EXPR.DGNLIB file into a MicroStation folder which is part of MS_DGNLIBLIST path (e.g. C:\ProgramData\Bentley\MicroStation V8i (SELECTseries)\WorkSpace\Interfaces\MicroStation\default ). Proceed similary with all DGNLIB files you want to in use in your default editing  environment.
• Ensure editing capabilities: To enable customization of an open DGN file (DGNLIB file) which is not a configured DGN library (not contained in MS_DGNLIBLIST) you can add the following line to your configuration file (.ucf): _USTN_CAPABILITY <+CAPABILITY_UI_LOADFROMACTIVEFILE. If you add it to msgeo.ucf or untitled.ucf you will be able to customize each DGNLIB file that you open by double-clicking.