There are three notes to learn on the second string, the open B note, the C note on the first fret and the D note on the third fret.
The open second string is a B note. This B note is written on the middle line of the staff.
Exercise 10 introduces the open B note. It is good practice to reverse the order of your right hand alternating fingers as shown in the following exercise. Practice all the following exercises and melodies both ways.
The note on the first fret of the second string is a C note. Use the first finger of your left hand to fret this note. This C note is written in the third space of the staff.
Exercise 11 introduces the C note on the second string.
The note on the third fret of the second string is an F note. Use the third finger of your left hand to fret this note. This D note is written on the fourth line of the staff.
Exercise 12 introduces the D note on the second string.