Start by drawing the face and mouth. It looks like an hourglass. The top part of the face is wider than the bottom part. Be sure to add another line on the bottom for the mouth.
Next draw the head and ears around the face. The head is pointier on the bottom and wider on the top. The pointy ears are on the sides of the head.
Now draw a line down from the head to make the chest. Add the arm. The monkey's arm almost looks like your own arm. It is wider at the top than at the hand. Make sure you draw fingers.
Continue the belly line to the back leg. The back leg is the same width as the arm but a bit longer. Don't forget the toes on the foot.