The SQLite database is only for single users only. You can choose between using an Access database, MS-SQL or MySQL or PostgreSQL. Open XTAdmin and create the new database you need. Please find details in the chapter "Database connections"
In case you want to have a look at the entries in your database, you need to install the SQLite plugin for Firefox. This allows you to open the database directly. Please do this only, if you really know what you are doing.