let's say, I'm running Tixati at my home and I have something to download when I'm not home so I can open Web Interface and add new download. I opened Web Interface option in setting but how can I access it? I can access "localhost:8888" in local PC, or "ipAddress:8888" in local network. But how can I access from internet? Is it possible?

It's possible if your PC have a public (non-private) IP address.