• download qdPM_upgrade_package_from_6.0_to_7.0.zip 
  This file contain only qdPM core files, there is no configuration files and symfony core in this package so you can just rewrite all files.
• download qdPM_db_updates.zip  and run run sql query  from_version 6.0_to_7.0.sql
• go to menu "configuration->tasks->tasks columsn" and configure tasks coulmns list
• clear ‘core/cache’ folder (remove all files/fodler under this folder)

Note: in qdPM 7.0 all configuration, that was in app.yml file, moved to web (you can found it in menu 'configuration->qdPM') and it means after upgrade you have to update qdPM configuration