Check if MySQL server is up and running. You can do it in cPanel/WHM of your server or by executing "mysqladmin status" command via SSH.
Double check thay all database settings (hostname, database, user, password) are spcified correctly. Make sure database user have appropriate access privelegies for your database. You can check and modify this settings in Database section of your servers cPanel/WHM.
Locate and remove following configuration files on your server:
Open url of your Slider Editor in browser to start over installation process.