To play the note B, pick the open second string.
This is a B note. The note B is written on the middle space of the staff.
This black box is a half rest. It means two beats of silence. To play this rest, count for two beats without playing any note.
The letters above the songs are chord symbols. Do not play them now.
The small numbers at the start of each bar are called bar numbers. They are used to count the bars.