So to balance the gimbal you want to add weight to the front of the lens because by default, the camera will be back heavy once the lens has been installed.
To do this, DJI have released what they call a 'balance ring' which is like a UV filter but without the glass... Essentially it's just a metal ring that can screw on to the front of your lens (it comes as standard with the DJI 15mm) and is heavy enough to balance the gimbal (sort of). Another way to balance the gimbal instead of using the balancing ring would be to use a UV filter, polarizing filter or ND filter.
The balance ring can be taken off of the DJI 15mm and put onto the Olympus 12mm with no problems as they both have the same filter thread size.
However, this is not the case with the Olympus 45mm as it has a 37mm filter thread so you have a couple of options, you can either buy a new set of filters that have a 37mm thread size OR you can simply buy a 37mm - 46mm step up ring which will then allow you to use your 46mm thread sized filter fit on your Olympus 45mm.
On a side note - DJI will be releasing more balance rings in the future to accommodate these new lenses with their varying thread sizes.
I hope that made sense and helped!