If the priority light is not on, press the [Priority] button. You cannot change settings unless the priority light on your specific remote is lit.
If you provide more context or details about the TGC BC-90-1H, such as its purpose or the field it's used in, I may be able to offer more specific guidance or point you in the right direction.
Note: Since I don’t have the official proprietary manual, this guide synthesizes common specifications for this model. Always verify with your physical manual.