This video below is a great way to see how you can play snake!
However, one aspect it does not include is the arrow key usage, simply use your arrow keys as listed below.
right
snake head turns right
left
snake head turns left
up
snake head turns up
down
snake head turns down
The purpose of moving the arrow keys are to make the snake "eat" the spawned foods, if so, the snake slightly grows longer. Which means, if the snake eats all the foods spawned, leaving no space in the "grass", the player has won.