This is the hadith you are referring to:
There is no one whom Allah will admit to Paradise but Allah will marry him to seventy-two wives, two from houris and seventy from his inheritance from the people of Hell, all of whom will have desirable front passages and he will have a male member that never becomes flaccid (i.e., soft and limp).
ما من أحد يدخله الله الجنة إلا زوجه الله عز وجل ثنتين وسبعين زوجة ثنتين من الحور العين وسبعين من ميراثه من أهل النار ما منهن واحدة إلا ولها قبل شهي وله ذكر لا ينثنى
The dwellers of hell in the translation you are referring to means people who ended up in hell, while their wives ended up in paradise. The wives of those 70 men are married to a believer in paradise.
This is for the sake of clarification only. As you can see from the link, this is a da'if (weak) hadith.
This hadith in Sunnan ibn Majah was narrated by Muhammad ibn Yazid, through Hisham ibn Khalid, through Khalid ibn Yazid, through Yazid ibn 'Abdul-Rahman (his father), through Khalid ibn Ma'daan, through Abu Umama to the Prophet. Khalid ibn Yazid ibn Abi Malik is very weak, and none of his hadiths are considered authentic.