Firstly make sure you have XBMC installed, you can get it from here: http://xbmc.org/download/
After installing, if you run XBMC and goto Settings -> Services -> WebServer and enable allow control of XBMC via http and take note of the port(default 8080).
Now get the mobile app on your phone or ipad, there is plenty of apps that allow the remote control of XBMC. Now add a server and add the ip address or computer name and port, so if you followed my other guide about setting up a media server then you should be able to fill out the computer name and port(servername.local and port:8080).
So now we can control XBMC remotely, but now we need to setup Utorrent, Sickbeard and Couch potato. Goto Programs -> Add-Ons and then Get More. Then install and enable UTorrent, Sickbeard and Couch Potato.
If you haven’t installed utorrent, sickbeard and couch potato outside of XBMC, then this would be a good time to do so. XBMC will have the default settings for the apps and you should be able to install all the apps apart from utorrent where you will need to enable http server so that sickbeard and couch potato can send the respective calls to download.