To play the Bbsus2 we use the index finger to play the first fret on both the E and A strings. Make sure the finger is in the right position so that both strings ring when played. Once you have that in place swing the ring finger up to the third fret of the G string. Keep that top joint perpendicular so you don’t interfere with the open C string. Check to see all strings play and then strum! The final result will leave your hand a little contorted and may feel a little uncomfortable for a beginner.