Welcome to the Joomla forums.
You may want to read the Forum Rules
as this give some indicators towards how to make a post.
How & where are you installing Joomla?
Local (XAMPP, WampServer, MAMP, LAMP, or other) or remote (dedicated, shared, or VPS) host?
Apache or IIS?
MySQL or other database?
If you want help then you must help yourself by providing the information necessary as all situations tend to be different
The above all said it is likely that you are not entering the correct information in the required fields.
If installing on a localhost stack such as XAMPP, WAMPServer2 or MAMP then you need to enter the following information:
- Username = root
- Password = blank (leave it empty; UNLESS you have changed the security settings during the installation of the stack)
- Database Name = (just enter a logical name that relates to the name of the site you are creating)
- Host = localhost
If on a remote host then your host will have provided you with the necessary information or it will be available from their control panel.
- The MySQL database user = xxxxxxx; // whatever the name of the user with full permissions for that database
- The MySQL database user password = xxxxxxxxx; //the password for that user
- The MySQL database host = localhost; //the default name when DB is on same hardware as the Web server. If at a separate location or configured differently then this will be the URL or IP address of that location.
- The MySQL database port = 3306; //the default MySQL port number (where needed)
- The MySQL database type = mysqli //the default requirement for Joomla 2.5
- The MySQL database name = xxxxxxxxx//whatever you called the database
- The MySQL database prefix = xxxxx_ //whatever you want the Joomla tables to be prefixed by.
If you are creating the Joomla! site on a remote host, then they will either have provided you with all these details when you registered with them OR you will need to create the database in accordance with the host's instructions.
If on a remote host then please run the Forum post Assistant
to provide the information to help us try and resolve the issue.