If you have VNC or telnet access to your hosted site, you can run the isql program from the command prompt. Remember to type GO on a blank line after you enter your SQL statement. Oracle's command-line client is called sqlplus. If your site is hosted on a Unix system, you should be able to use sqlplus from the command line. After you've created the initial structures in your database, begin writing applications that will use the structures to store data.
Most applications use an API that provides function calls specific to the database in question.
Many database server APIs follow a simple paradigm whereby you must first allocate a database handle, then create a query, execute the query, and finally, receive the resulting data set. The result set, in its simplest form, can be thought of as an array. Each element of the array holds data for the fields you specified in the query. For instance, an array element may contain a name, phone number, and shoe size from a customer record in your database. If your hosting provider didn't install DBI, chances are they installed a library for your database.