Hello,
Can you please tell me how to create a MediaWiki? I don't know how to do that. There are no links to do that.
Topic on Project:Support desk
You mean create your own wiki? See Manual:Installation guide.
U only have to install media wiki??
Indeed, its a computer program like any other (So is any other website on the internet).
Some people offer hosted MW (where they take care of those details for you). Some charge for it, while others offer such things for free (Typically the free one's either require adverts and/or require the wiki to be on a topic of interest to the general public) There's a bunch listed at w:Comparison_of_wiki_farms, but there's many others not listed there you can find by googling.