You can set WP_DEBUG to false in your wp-config.php file. This won’t fix the problem however It will only hide ALL the errors generated by it and any other plugins.
The warnings mean the second and third parameters in the ufwp_widget_text() function have no defaults set.
If you are using this function in your own code be sure to pass all three arguments.
If you are not, you will want to make sure the plugin is up to date; it’s possible the error was already fixed by the developers. If the issues still persists you can reach out to the developers to report your issue report the issue on the plugin’s github repo.