I understand that I need to configure database address in the TNSNAMES.ORA file but where should I put this file?
UPDATE
I defined the $TNS_ADMIN variable, created the TNSNAMES.ORA file, added new connection and restarted my machine. Unfortunately, the Database list in Oracle Logon remains empty.
However, the following error occurred when I was trying out various options in PL/SQL Developer:
Initialization error
SQL*Net not properly installedOracleHomeKey:
OracleHomeDir:
What is SQL*Net?