If you want to know when Jesus mentioned hell...
Read Matthew Chapter 5, (Also when Jesus gives the Beatitudes during the Speach on the Mount).
21"You have heard that it was said to the people long ago, 'Do not murder,[a] and anyone who murders will be subject to judgment.' 22But I tell you that anyone who is angry with his brotherwill be subject to judgment. Again, anyone who says to his brother, 'Raca,[c]' is answerable to the Sanhedrin. But anyone who says, 'You fool!' will be in danger of the fire of hell.
He mentions it again in Verse 29, in the "If your eye offends you, pluck it out.." portion of the same. Therefore, let's just say that Jesus talked about it quite a bit during the Sermon on the Mount.
In Matther Chapter 7 he goes into how much easier it is to get into Hell. That's when he talks about the "highway to hell" being broad.
In Chapter 10, he talks about how god can destroy your body and soul in Hell so you are not to fear those who might kill your body.
It was a pretty consistent theme in things he spoke of.