EC2 instances uses SFTP and not FTP. Since you do not have a password. The easiest way to configure the WordPress update is via command line. SSH into your instance and enter the following.
sudo chown -R www-data /var/www/wordpress
sudo chmod -R 755 /var/www/wordpress
Thank you for sharing! Many web developers are into WordPress. Although it is easy to use and modify, having in-depth knowledge in coding and web development would help on maximizing the features of this platform.