JRPass activation

Hello,
We will be in Tokyo on Aug 23 and are planning to go to Osaka on the 28 of Aug and will return to Tokyo on 2 of Sept. We bought a 7 days pass. We have to exchange the Order for a JRPass. When do the 7 days starts counting down, is it at the time of exchange? or at the time of first use.

Do you have a link for Train schedules, connections and routes. It seems too complicated for first timer to use train. I have seen on Youtube that other people have app that tells them which train and connections to take to get to their destinations.

Hope you could help to ease our travel within Tokyo, Osaka and Kyotu.