You have created a new database, but have not yet imported the 'cacti.sql' file. At the command line, execute the following to continue:
mysql -u cacti -p cacti < cacti.sql
This error may also be generated if the cacti database user does not have correct permissions on the cacti database. Please ensure that the cacti database user has the ability to SELECT, INSERT, DELETE, UPDATE, CREATE, ALTER, DROP, INDEX on the cacti database.