Book tickets with JR pass

Hi,
My friends and I are traveling in May to Japan and have each purchased a JR 7 day pass. We plan to travel to Osaka and Kyoto for a day each during our trip. How would we go about booking tickets for the train with our JR pass?

Our desired travel dates is May 20 from Tokyo to Osaka, then May 21 from Osaka to Kyoto, then back to Tokyo either later that evening on May 21st or in the morning on May 22.