Providing an exact page number is going to be difficult without knowing exactly which edition of The Crucible you are looking at. In my copy of the play, Abigail accuses Tituba on page 16 and again on page 43. The first location is just after the Putnams show up at Parris's house. The notion of witchcraft has been broached, and Parris is quite averse to alerting the town to this possibility. The Putnams are convinced that a "murdering witch" is loose, and Ann lets Parris know that she asked Tituba for help speaking to her dead children. Parris then knows that Abigail was lying earlier. She and the girls were doing more than just dancing. They were conjuring spirits, and Parris accuses Abigail of this; however, Abigail denies it and accuses Tituba.
Parris, to Abigail: Then you were conjuring spirits last night.
Abigail, whispering: Not I, sir—Tituba and Ruth.
The second time that Abigail tries to pass suspicion off of herself by accusing Tituba occurs shortly after Hale starts to aggressively ask Abigail exactly what was going on in those woods. Hale grasps Abigail and asks her if she called the Devil, and Abigail says that she did not. Abigail then says Tituba's name twice. Hale continues his line of questioning and repeatedly asks Abigail if she drank anything from the kettle. Abigail is a smart girl, and she knows that she has to get the attention off of her. Tituba enters the room, and Abigail cries out that Tituba forced her to drink blood.
Abigail: I never sold myself! I’m a good girl! I’m a proper girl! Mrs. Putnam enters with Tituba, and instantly Abigail points at Tituba.
Abigail: She made me do it! She made Betty do it!
Tituba, shocked and angry: Abby!
Abigail: She makes me drink blood!