Bismillah. Alhamdulillahi rabbil-'alamin was-Salatu was-Salam 'ala Sayyidil-Mursalin wa 'ala 'Alihi wa Sahbihi Ajma'in.
So the question is How did Adam and Hawwa multiply?
I'd like to know both Sunni and Shia views.
Adam and Eve multiplied like any other human today, by the process of sexual reproduction which results in giving birth to children. Perhaps you are asking about subsequent events, such as how their children multiplied or to whom they married.
This is an issue on which there are different reports. The widely accepted story is that the children were born in pairs and a male married any female who was not his twin. Another story is that the children married women from the Jinn and Hoor al-Ayn - this report being attributed to Imam Ja'far bin Muhammad al-Sadiq (see Fath al-Bari 6/369). The Sunnis lean towards the first report, while the Shia sources I have seen seem to lean towards the second one.