writing from mental hospital

[Mister Agenda]

I am atheist.
I committed a crime and pleaded not guilty by reason of insanity.
and now I am stuck in mental hospital for life.
give me some advice.
it is a very dangerous place to live in.
what should I do ?

Depends on the laws of the country you're in and your actual mental state. If you are actually not insane, you can try to make a case that you're cured. Depending on the country, if you succeed you could be back on the street or serve a regular prison sentence.