My car shakes on freeway it has emission system light on it wouldnt start

What is your question?

i was driving on the freeway my car started to shake. i pulled to the shoulder and turned it off. when i turned it back on again it would just die so i rev the engine and alots of white smoke came out from exhaust so i turned it off. now it has a sign of emission system. what should i do and how to fix it?