I have uploaded Civicrm 5.12.0 on a Drupal 7.65 site via FTP. After upload was completed, I attempted the installation script, but nothing happened. Is there a step that I forgot to do or wasn't aware of?
Look at the error log file of the webserver (probably apache2). If you see an entry like
PHP Warning: POST Content-Length of 21426352 bytes exceeds the limit of 8388608 bytes in Unknown on line 0
you will have to adapt the /etc/php/7.2/apache2/php.ini file in order to rise the value of two parameters to v.gr. 32M:
upload_max_filesize = 32M post_max_size = 32M
Don't forget to restart apache after updating php.ini at the command line interface by issuing:
sudo service apache2 restart
Installing CiviCRM on Drupal 7 guide is on the following link https://docs.civicrm.org/sysadmin/en/latest/install/drupal7/ . From your question is quite difficult to tell what you have done or what the issue can be (did you check Drupal db settings, system requirements etc)? What are the error messages if any? Did you test locally before attempting in production?