Do you have a full-time connection to the Net from your PC??
Do you have a static IP address (unchanging)?
Is your app already web-enabled??
What's your OS? - Win2k Server recommended for live sites
Once these questions are answered in the affirmative, you are ready to get started.
If you just want to give web demos, you could just set up Personal Web Server on Win98 with your web-enabled app. You could also just give out your IP address once your on the Net meaning that, for demos, you could use a dynamic IP address (even dialup)...

>Where do I start to make my app accessible through the web from here on my PC?