Write to device help

I have the following in my ESPhome configuration yaml file to read the Over Voltage value from my Inverter

 - platform: modbus_controller
   modbus_controller_id: srne1
   name: "Overcharge voltage" #name for HA
   id: srne_overcharge_voltage #id for HA
   register_type: holding
   address: 0xE008 #register address (see modbus manual)
   unit_of_measurement: "V"
   accuracy_decimals: 2
   device_class: Voltage
   state_class: measurement
      - multiply: 0.4   

I have a dropdown created to change values for different voltage values

Can you please tell me how to write the value selected by the dropdown to the inverter registry?