Okay, the easiest way for you to do this is via a terminal.. its not the big scary monster people think it is, just follow this and you will be fine !
Open a terminal click applications then accessories then click terminal.
Now type the following (you will be prompted to enter your password)
Code:
sudo kdesu /etc/apt/sources.list
This will open a text editor.. scroll to the very bottom and paste this in.
Code:
deb http://ppa.launchpad.net/bortis/ubuntu hardy main
deb-src http://ppa.launchpad.net/bortis/ubuntu hardy main
Now save and close this file, you have just added the repositories you need to do a simple install.
now in the same terminal type this.
and finally type this
Code:
sudo apt-get install transmission
Congrats, you now have transmission installed, and there should be a shortcut under applications/internet/transmission.
Any probs let me know.