Check out Dr Liana Mawer's website. There is an article about introducing a new cat into a household, as well as keeping peace in a multi-cat house at this link (as well as lots of other great pet advice!):
http://www.drlianamawer.ca/index.php?id=catbehaviour
Also, please do not let your cats outdoors. As well as being against Brandon's bylaws, it is dangerous for the cat - it could get run over, poisoned, injured, treated badly, get in fights, etc.