JR Pass for 7 days

Hi All

I have purchased a 7 days JR pass
My itinerary as following by using JR pass:

1. Mar. 19 travel from Tokyo to Osaka
2. Mar. 20 and Mar. 21 sightseeing within Osaka
3. Mar. 22 travel from Osaka to Hiroshima for sightseeing Hiroshima and Miyajima island
4. Mar. 23 travel from Osaka to Kyoto for Sightseeing
5. Mar. 24 travel from Osaka to Nara for sightseeing
6. Mar. 25 travel from Osaka to Tokyo for sightseeing
7. Mar. 26 leaving Japan

Please let me know how can I use the JR pass and when do I need to buy extra fare for the trips.

Thanks you in advance.

Dung Hoang