My friends daughter is in nepal an he and his wife both are here. She is lil over than 4 years. She had a visa to us before but my friend thought he would go first and settle down and then bring his daughter. But now he doesnt know how to apply for her. Anyone has any idea about this matter, it would really help.

He can file family/relative petition. 

Category of unmarried sons and daughters of permanent residents for immigrant visas
May want to give visitor visa a try as well for whatever its worth as the other process may take longer

consult a lawyer, since she in nepal, it will be bit difficult to process from here

next time have baby over here, no haassel in visa stuffs, :)