First of all, if you are merely uploading a file, you may be able to do that with an FTP client or your hosting control panel's file manager. This would bypass the PHP setting limitation entirely.
Most hosting accounts do not come with a php.ini file. If you want to change some setting, you normally have to create the php.ini file yourself. It often lives in the site root (/) but might be placed elsewhere (such as above /, to prevent unauthorized access), and an entry placed in .htaccess (usually suPHP_ConfigPath /full/dir/path/to/file) to tell PHP where to find php.ini. Your host (LP) will be able to tell you any such details. If you're using a Windows server, though, the details will be different.
Before and after changing php.ini, run the following script:
<?php phpinfo(); ?>to see what the old setting was, and make sure the php.ini does change the desired setting.