My lawnmower is leaking oil?

well stupid me i was trying to fix the belt that spins the blade cause it popped off , well i couldn't really figure it out so i tipped it on it side to see if i could do it better and i got it to go on but when i tipped it back over oil was leaking out and now every time i start it smoke comes out the left side , and oil comes out , so what is exactly wrong with it