From Hiroshima to Kyoto ?

If we exchange JR vouchers arriving in Narita is it right that you may start using them at a later date ?
I mean its not automatically starting once you have your pass ? Must a date be given as to when you will start using them ? Furthermore if I know the date I will use them , is it possible to have the ticket issued right away or only have it issued the dates you are going to use them ?
I am somewhat confused about it may I say .

Is there only one train to be taken to reach Kyoto from Hiroshima or is there more ?
If there is more than one , where must it be taken along the way ?

From Kyoto inner city wich subway station to go to to reach Nara , Kobe and Osaka by train as well as Milho Museum may I ask ?

Thanks to anybody who could help .

Gerald