Alien had a felony conviction in 1991 and served 2 years in USA correctional institute, now would like to apply for green card. Was previously married to US citizen and has on child, who needs his support
Additional information
Is in USA illegally BUT would like to apply for green card, What would he have to do to be successful
It is hard to give a specific answer with the information given. But depending on the lawfulness of his original entry into the US, and the type of felony conviction, and of course whether he has a way to adjust status now (perhaps the child is over 21, perhaps he is now married to a USC, etc.) he may be eligible for a waiver (e.g. under 212(c)) that would "forgive" the felony conviction.
Immigration is highly technical. You have to meet very narrow statutory requirements. Thus there is seldom a "general" way to apply for a green card for a person in this alien's situation.
Most importantly - don't file anything without consulting a competent attorney. It is likely that doing so will only result in the commencement of removal proceedings.