Soon (not available as of June 2013) we will have a web based tool to add support for your infrared device without any technical skills, and which will also support learning infrared codes.
In the meantime, you will need to create a Luup plugin by hand as explained here: Luup Plugins. A Luup plugin for an infrared device is no different from any other plugin. You still create a UPnP device file, one or more service files which contain the actions the device implements (i.e. on, off, volume up, etc.), and a Luup implementation file. The only different is that the XML tag you will use in the implementation file is called "<IR>" and contains the infrared code in Pronto format. Until we have the learning module going you can find infrared codes in Pronto format for many popular devices at remotecentral.com. Also, most IR learners have a software utility to learn the codes and show them in Pronto format.