Go to File, Print. Then follow these steps:
First, select the slides you want to print.
Then select 'Scale to fit paper'. Now you are ready to print!
By the way, did you know you don't HAVE to print in color? I save on ink by printing mostly in grayscale. Just select 'Grayscale' from the drop down menu (shown above).
I hope these tips help you out! Happy printing!