Erro database

i had installed piwik in my host. then i had designed a signup form but it doesnt work because of database connection error.
(error was " Connect Error: Access denied for user ‘seilani_ad2’@‘localhost’ (using password: YES)")
when I change the database( a database that is not used by piwik) it work.
so whoud you please help me that how i can change piwik in order to not makes error for database connection.