Indexing with interMedia

I know I am a newbee to Oracle but still I ask my question and hope some of you can help me in the right direction.

I have a database table that contains a BLOB field that contains documents of different types. PDF,TXT,TIF etc. I want to index the content of the field so that I can do a free text search in the document.

Some of you mention interMedia, and then my question is : How do you set up interMedia ? I have read a lot of documentation on the net (otn.oracle.com) but I have not found a document that tells me : How do you install interMedia (I have installed it from the CD but when I start it and log on to my oracle service and want to create an Index it tells me : Oracle interMedia was not installed with this database.Install Oracle ... )
How do you set up interMedia to index the field in the table ? How do you search the index ?

I really hope someone can help me with this.

-- 
Regards
Robert Vabo
Gecko AS
www.gecko.no