2
Did you follow the help here?
http://xoopsdocs.net/modules/docs/
You may have forgotten to create an empty DB for XOOPS to write to... you have the wrong username/password/path or somecombination of the above. You may also have a bad mainfile.php.
All hard to guess without the exact error message.
I recommend you start with the documentation though.
Pax vobiscum,
...mark
may the road rise to meet your feet!
http://treemagic.org