You have two choice!
1.using Discuz!EXP,but you need to switch on the computer all the times! And
If yoiu want people visit your forum,you need to send your computer's IP address to them!
2.go
http://www.discuz.net to download the file(Discuz5.5)>>>Find a hosting web site!>>>update all files on it!>>>open(
http://yourwebsite.com/install.php)to install!>>>finish!