Install trakt from the XBMC addon repository:
- If you don't have XBMC installed yet, download it here
- In XBMC, go to Settings » Add-ons » Search and search for trakt
(If it doesn't show up, try refreshing the xbmc.org repository so it gets the latest listings)
- Select the trakt plugin and choose install
- After installation, open trakt again and select configure
- Enter your username, password, and change any other settings as needed
- Select OK to save your settings
- Watch something and see it show up on trakt!