The events that your question ask about occur toward the end of the Act 2. The setting of Act 2 is the Proctor household, and a lot happens during this act. John and Elizabeth discuss whether or not John should go to the court and tell what he know about Abigail and how he knows it. Hale shows up to sort of vet John and Elizabeth. He announces that Rebecca Nurse has been mentioned in the court proceedings as having some business with the Devil. John and Elizabeth can't believe it.
Then Cheever and Herrick enter the Proctor household. They are there to arrest Elizabeth. She has been accused of witchcraft by Abigail Williams. The two men are there to arrest Elizabeth and find a poppet (doll) that has a needle stuck in its belly. The poppet supposedly serves as evidence that Elizabeth sent her spirit upon Abigail to stab Abigail in the stomach.
Cheever: 'Tis hard proof! To Hale: I find here a poppet Goody Proctor keeps. I have found it, sir. And in the belly of the poppet a needle's stuck. I tell you true, Proctor, I never warranted to see such proof of Hell, and I bid you obstruct me not, for I -