Go for a walk around the room. Look carefully at how your legs move, one and then the other. Now do the same with your fingers "i" and "m" on your knee. Do it slowly and watch how when one finger is in front, the other goes to the back.
This style is used for our rest stroke, called alternating. With your thumb resting correctly, place your "i" finger on string number one (E string) as indicated in the diagram.
Pull the finger across, using the tip of the finger and let it come to rest on the second string.
Now bring your "m" finger to the E string and pull it across to the second string. Like the "walking" discussed earlier, at the same time bring the "i" finger back to the first string.