you may need to sudo. ubunto probably doesn't let mere mortals use chmod.
You'll only need to use sudo if you as a user don't already have write permissions to the file. If, as it sounds in this case ,you've downloaded the file yourself, then you should have the required permissions.
You'll only need to use sudo if you as a user don't already have write permissions to the file. If, as it sounds in this case ,you've downloaded the file yourself, then you should have the required permissions.