sudo apt-get update
sudo apt-get install transmission-daemon
Create required directories on your NAS storage (path to storage is assumed as /media/NASDRIVE)
mkdir -p /media/NASDRIVE/Torrent_inprogress
mkdir -p /media/NASDRIVE/Torrent_complete
Transmission by default runs with user "debian-transmission", as it is recommended not to change this due to security reasons. In our setup the NASDRIVE has the permission set as 770 for pi : pi. Thus we will add user "debian-transmission" to "pi" group to give rwx access on our NASDRIVE. You can go ahead and modify this step as per your security requirement, but just make sure your torrent download directories are having rw access for "debian-transmission" user.
sudo usermod -a -G pi debian-transmission
While most of the parameters are self explanatory in the conf file, you can use the file given below, except for modify the parameters download-dir, incomplete-dir, rpc-username, rpc-password
Note: rpc-password will automatically converted to hashstring on saving the file
sudo nano /etc/transmission-daemon/settings.json
Do not restart, It overwrites the configuration file in that case
sudo service transmission-daemon reload
Open web browser and hit http://your_raspberry_pi_IP:9091
Enter the user id and password you've configured, and viola!