Since UPlay requires Xbox Live... there is no free method to get you online, you'll have to bypass all the security checks made by the Xbox Live servers and for that there is a service on the web which charge you for it...
We don't really like ppl that use this service around here tho, mainly because most ppl that want to use it are ppl that are only interested in modded games which give them a unfair advantage which messes up the game for everyone else...