You are essentially looking for an online application form.... someone fills in the form data which is then added to a database.... you then have pages which query the database for non-expired events and show the detail.
You sound like you have little knowledge of web development, so with that in mind, your best bet is to either jump in at the deep end and learn
PHP,
ASP or
ASP.NET or.... hire someone to do this for you.
It may be possible for an existing 'events' application to be modified for the purposes you need it for, but that will most likely require development knowledge.
Please give us some feedback and I can direct you further.