Once you have it, you can use the web admin to make device templates for your AV equipment, like your cable box, your TV, your amplifier, etc.
You make a device template for each, making sure to specify the right manufacturer and category for each device.
We have IR codes for many manufacturers, so there is a chance that there is a set of codes that will work in the database. select and try each one to see if you can get it to work. (Make sure you have the UIRT's embedded transmit selected as the target device, and make sure when you hit T that the UIRT blinks.).
If you are able to find a set of codes that work, then you won't have to train anything for that device.
If not, no big deal, create a new code group, and specify what buttons/etc are on your existing remote to control the device. You can then train each one, by placing the remote in front of the UIRT, and pressing the button a few times until it says it has been trained. You can then test the code to make sure it works.
Once you've done this, you can use the setup wizard to set up the devices and tell linuxmce how they are connected together. LMCE will then control the devices.