Your hosting company should have provided you details of how to upload files to your server. Look on the control panel for help.
Check on your initial communications with them for a FTP address, Userid and Password, then use, for example FileZilla Client to upload you app to the server. They prpbably also have a phpMyAdmin or equivalent for you to upload a backup of the database if you have one.
I assume your site is PHP? With a MySQL database? If so, you need to export the database from phpMyAdmin, then import to the new database. Then you need to update the SQL connection information in your site's PHP.