Download the connection script pgpro-repo-add.sh. You can also do it using wget:

  $ wget --user your-username --ask-password https://repo.postgrespro.ru/ora2pgpro/keys/pgpro-repo-add.sh
  

Run it with the rights of root. If your distribution is supported, the repository will be connected. Note that for a Debian-based system make sure to connect not only the main section but also the contrib section since it contains the required libdbd-oracle-perl package.