To reset BMW airbag indicator on a BMW E92 coupe 3 series you must use a special tool for this warning light.
This is how it looks the SRS or MRS air bag lamp and the scanner with obd plug.
How do you see in the picture I use a BMW code scanner C110 whis works for Mini to.
To succeed you must follow the next steps:
Connect the C110 on the OBD plug which is located on the driver seat next to right foot if you have steering wheel on the same side.
Pres ok button.
Diagnose is the next step.
Now go to 3 series.
After that on section 3 you will find E92 go there and press ok.
Now you must choose body.
And select the ACSM this means crash safety module.
If you want to see why your airbag light is on select read trouble code, if you want to reset the air bag indicator select erase trouble code.
If you have any questions do not hesitate to leave me a comment.