Unified Remote is primarily designed to work with WiFi on your home network or using Bluetooth (due to performance and security reasons). However, it is possible to use Unified Remote from any mobile data, over the internet, as well.
It is highly recommended that you enable password protection in Unified Remote Server when using external connections. See this tutorial for more details.
If you are using Windows Firewall or any other security software you may have to enable public access to the ports used by Unified Remote Server (TCP/UDP 9512). See this tutorial for more details.
The most important part is that you enable port forwarding on your router. By default most routers do not allow inbound connections from the internet. How to enable port forwarding on your router is outside the scope of this tutorial. See http://portforward.com for instructions.
Next you need to find your external IP address so that you know where to connect to. You can do that either using the Unified Remote Server manager, visiting Whats My IP, or Googling "Whats my IP".