the instructions are pictorial and in german, and some bits are clear others are not.
my basic translation of them (after using google translate )
1. turn blowers on to full, turn heat up to max, set to air recycle, aim at the footwell leave for 10 min
2. put can in the supplied box, put in footwell aiming up the pedal vent, put A/C on, make sure its on recycle, i turned the temp down to min. set can off, shut door, leave for 10. i left it on the foor well setting but i think it showed to put it on windscreen, but don;t do it if it turns recycle off.
3. once can has expired leave engine to run for further 10 min with doors shut and previous settings.
4. open all doors turn engine off and leave for 10 min
5. job done