To configure your I2C sensors go to I2C tab and press add.
OpenPlotter will check the connected I2C devices and will show you a list of possible models according to their addresses. You can refresh this list pressing Reset or see the detected addresses pressing Addresses.
If your device is not listed and you know its address, select the model in add/update sensor field and write its real address.
Press OK when you are ready.
A list of features of your device will be added to the sensors list. Some features will have a Signal K key pre-assigned when its function is obvious. Some features with more than one possible Signal K key assignation will be blank.
Double click on the feature you want to edit to change its parameters.
Select the Signal K key that best suits your needs. If you have a temperature sensor, probably you do not need to send data every second. You can define this frequency in Rate field. If you think that your sensors could have any deviation you can correct it setting an Offset. Press OK when you are ready.
Go to any Signal K data viewer and check your sensors are sending data.