What is the connection between "Shuvu Banim
Rashi: The Navi teaches them how to confess - 'we came to You, for You are Hashem our G-d, and we served idolatry' (verse 23).
Radak (21): Hashem tells them to repent, and they say "we came."
Why does it say "Erpah"?
Radak: This is like Erpa with an Aleph at the end. We find that pardon is called Refu'ah - "Refa'ah Nafshi Ki Chatasi Lach" (Tehilim 41:5). Just like a cure heals an ailment of the body, so pardon with Teshuvah heals sin, which is ailment of the Nefesh.
Sha'arei Teshuvah 1:1: Even if they sinned greatly and acted treacherously, the doors of Teshuvah are not closed in front of them.
Why does it say "Hinenu Asanu Lach"?
Malbim: We are prepared to repent, but we do not know to where to return, for we do not recognize Your voice.