The Fall

33 What was the sin of our first parents?
Eating the forbidden fruit.

34Who tempted Adam and Eve to this sin?
Satan tempted Eve first, and then he used her to tempt Adam.

35 How did Adam and Eve change when they sinned?
Instead of being holy and happy, they became sinful and miserable.

Questions and Answers 33-35 in First Catechism https://www.gcp.org/ProductDetail.aspx?Item=020030