It doesn't even do that according to the description:
The PC version of this app only shows SMS texts from your mobile operator about your data plan (billing, data limits, etc.), and only on devices built for high-speed wireless data (LTE). It can also show messages you've sent and received from apps such as Skype via SMS relay. It can't send texts.
Seems absolutely pointless to me in terms of desktop functionality. I can't think of anyone who wants to see texts from just their operator and if you want to see texts you've sent via Skype then I see no reason why you wouldn't just use Skype itself.