Windows64bit-plsqldeveloper-install the easiest way

The easiest way to add a 32 Bit Oracle Client:

1.Download the Oracle 11g or 12c Instant Client(http://www.oracle.com/technetwork/topics/winsoft-085727.html).
2.Create an "InstantClient" subdirectory in the PL/SQL Developer installation directory.
3.Unzip the downloaded instant client into this directory.
4.Define a TNS_ADMIN environment variable and set it to the directory where the tnsnames.ora file of your 64 Bit Oracle Client is located (e.g. C:\Oracle\product\11.2.0\client_1\network\admin).
5.Define an NLS_LANG environment variable and set your language, territory and character set (e.g. AMERICAN_AMERICA.WE8MSWIN1252).
To set environment variables you can start the Windows Control Panel, click on "System", "Advanced system settings", "Environment Variables".