Bar lines are drawn across the staff, dividing the music into sections called bars or measures. A double bar line signifies either the end of the music, or the end of an important section of it.
This is the four four time signature. The time signature is written immediately after the treble clef. The top number of the * time signature tells you that there are four beats in each bar. The bottom number tells you that there are four quarter notes in one bar of music in * time.
You already know the note A. It is the open A (2nd) string. This time the note A is played in quarter notes. Alternate your bow strokes as you play.
The note B is written on the third line of the staff. The stem for the note B can go up or down, because it is on the middle line of the staff.
Play the note B with your 1st finger on the A string.
Try playing this example using Pizzicato. It is a good idea to practice all examples both arco and pizzicato.