The regeneration of Toyota occurs automatically, usually without the driver being aware that it is taking place. In the majority of cases, the process is carried out when the engine and exhaust system is up to normal operating temperature and the vehicle is travelling at over 40mph.

Just to add.......If the engine management has any fault codes like Glow Plugs fault the regen might not be carried out so, you need to make sure there are NO any fault codes stored in engine ECU............