Ok, let's explain this nice search engine.
There is three boxes where you can type some text in:
ハッシュ (hash) where you can search for a given hash
ファイル名 (file mei) where you can search for a given filename
ID where you can search for a given Share ID (lists all files shared by a particular username)
The line below let you select the delay since the file was added to the database, like less than 3 months ago or 1 year ago. I suggest to check the last button on the right, which means no time limit (it takes all files).
The link below let you toggle the search between Share and Winny.
You can also browse the database by category, but it's not so convenient as to search for a particular file.