How did adam and eve figure out the sex thing?

17 Then Satan said to him, "Lo, it is now some time since thou camest out of the garden, and thou knowest neither wickedness nor evil. But now God s says to thee, to take Eve who came out of thy side, and to wed her, that she bear thee children, to comfort thee, and to drive from thee trouble and sorrow; now this thing is not difficult, neither is there any scandal in it to thee."

BUT when Adam heard these words from Satan, he sorrowed much, because of his oath and of his promise, and said, "Shall I commit adultery with my flesh and my bones, and shall I sin against myself, for God to destroy me, and to blot me out from off the face of the earth?