I was about 7 weeks postpartum, probably could have much sooner but I wasn't ready emotionally. Just go slow and talk to your partner. I've heard some ladies say they needed lubricant so keep that in mind.
My Docter recommended 6-8 weeks. I felt ready around 5 weeks and attempted it, but it was uncomfortable and started to bleed again.
I would wait until your Docter clears you. You could have no bleeding and still have some healing up to do (that's what happened to me)