You asked about how to use an app and Acts 2. The app is working for you because you are reading it. I figured I had better focus on the Acts aspect of the two part question. Now that you are in the app and using it , there are plans you can select to read the Bible.
After Jesus was crucified, he revealed himself to many. He told the disciples and others to wait in Jerusalem. The Holy Ghost descended and people began speaking in a language they did not understand. When people started making fun and wondering what was going on, Peter explained that they had crucified the messiah. The men of Jerusalem were unsure what to do about the poor choice they made. They asked Peter what to do about it. Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins,...