it is not yet possible with the official LimeWire release, you may try a BT enabled test version

http://www.magnetdb.com/viewtopic.php?t=37
( make sure to read the big red warning)

or you may try a regular BitTorrent client like Azureus: http://azureus.sf.net (which has the drawback of not being able to connect to Gnutella and the immeasurable advantage of being stable)