It's very easy to install and use ... there is no programming needed, simply plug it in between the phoneline and your phone (as shown in the manual), and wait for unwanted calls to ring ... then press the BLACKLIST button to add unwanted calls to the BLACKLIST so that next time those numbers call, the unit disconnects those calls.  Optionally, if you have a list of unwanted numbers, you could add unwanted numbers to the BLACKLIST memory manually, but that's not necessary.