Transmission

Hi
I'm an italian guys, please be patience with my english.
I have got a raspberry pi model 2.
I would like to install trasmission in order to have a torrent server managable by browser.
I follow a guide ( http://guide.debianizzati.org/index.php/Transmission ) but i found some problem.
When all is installed and configured as guide ....i run a download of a torrent and after some minutes i had this error message and i can't close the download.
transmission-daemon Error:Permission denied
I surfed in internet and i found some suggestion, i followed but now i have another error.
Error: Unable to save resume file: Permission denied
I'm using last version of Raspbian Jessie and, from oldest versions, there is a difference.
When i connect an external usb driver , where i would like to save complete e incomplete download, it was mounted automatically in /media/pi/New Volume/ , on oldest versione mount was manual.

Do you have a clear complete guide to install transmission on raspbian or a suggestion to fix this problems?
Thanks