I have a 3D file that I need to attach into my 2D MicroStation file
This can be achieved from the Reference Attachment Properties dialog when attaching the 3D file as reference to the 2D DGN.In the dialog (see image below) under Orientation there is the option 'Standard Views'. If this section is expended, by clicking the '+' sign, there are several standard view options to choose from.For attaching the 3D file in Front View, simply select 'Front'.
When the 3D file is already attached, there is no need to detach and attach it again to select for a different View.In this case just open the Reference Manager, select the reference file that need to be changed.Go to the column 'Orientation', click on the current orientation and change to the desired view (see image below)