Petrol webastos are not an unicorn I also own one...

I would suggest: contact the bmw customer service, they will send you a pdf version of the manual or order one at your local dealer: part number should be 01420156408 for the french one - should be around 50 €

Operation via remote: press ON for about 2 seconds and it will start (LED will light and then start to blink as long as the heater is working. If it only blinks about 3 or 4 times and turns off the remote couldn't connect to your car (distance too long, ...)
To turn it off, simply press OFF for about 2 seconds

Operation via MID or Navigation is also possible (via timer), which one do you have?

Reason for the smoke is that it wasn't started for a while probably?