Services|Bittorent

Here you see an overview of the setup page:

Setting	Input	Values
Peer port	Text field	Numeric port number for peers to connect on (should be mapped from router if possible)
Download directory	Text field	Absolute path for transmission to save downloaded data to by default (Transmission WebGUI or client can override)
Configuration directory	Text field	Absolute path to transmission configuration/control directory if using embedded, without setting this to a writable location, transmission will forget torrents and torrent progress on each reboot
Port forwarding	Checkbox	if checked, enables port forwarding via NAT-PMP or UPnP. (may help with some routers)
Peer exchange	Checkbox	if checked, enables peer exchange (PEX). (can help finding other peers not offered by the tracker)
Distributed hash table	Checkbox	if checked, enables distributed hash table. (can help keep torrents running if a tracker becomes unavailable)
Encryption	Selectbox	Encryption choices: tolerated, preferred, or required
Upload bandwidth	Text field	The maximum upload bandwith in KB/s. (empty means not limited)
Download bandwidth	Text field	The maximum download bandwith in KiB/s. (empty means not limited)
Watch directory	Text field	Absolute path to watch for new .torrent files. (optional)
Incomplete directory	Text field	Absolute path to store incomplete files. If blank, in-progress and incomplete files are stored in the download directory.
User mask	Text field	(optional, 0002 by default) overrides the default file/directory permissions modes for newly created files/directories Octal umasks
Extra options	Text field	Extra options (usually empty). http://trac.transmissionbt.com/wiki/man/transmission-remote

There is additionally an administrative WebGUI that can control Transmission:

Setting	Input	Values
Port	Text field	Numeric port to use
Authentication	Checkbox	if checked, requires username/password for access. Otherwise, allows anyone to access
Username	Text field	self-explanatory
Password	Password field	self-explanatory
URL	n/a	A link to the WebGUI (for convenience)