Not having dealt with the multipar symbol yet, I'll ASSume that the unit is oriented lenses up when you drop it into a drawing.
You have to edit the orientation of the fixture in question in the resource browser. Get your drawing's name in the drop down menu, scroll down to the unit you want to re-orient, right click on it, edit 3D component,(this will get your light in a window by itself). You're going to want to change the view to the side (right or left- doesn't matter)Right click on the light, rotate.....flip vertical.....exit symbol. If you're doing an angle other than 180, you'll need to know that before you flip the light. If you have the same fixture with more than one orientation (angle), you'll need to duplicate the symbol for each. From then on, in this drawing, you'll be able to drop the fixture in at the angle you want.
Remember, everything happens from(your drawing)inside the R.B.
Oh yea, make sure you have the latest updates. I've found out that some things are possible in 12.5.3 that weren't in earlier versions.
Bob