Use the TADPhysPgDriverLink component to link the PostgreSQL driver to an application. In general it is enough to only include uADPhysPG unit into your application uses clause. 

The TADPhysPgDriverLink component may be used to specify:

• VendorHome - the PostgreSQL installation root folder;
• VendorLib - the name and optional path to the PostgreSQL client library.

All properties have default values appropriate for most case. To have an effect all property changes must be performed before first connection through this driver or use the Release method.

TADPhysPgDriverLink = class(TADPhysDriverLink);

Configuring Drivers, Connect to PostgreSQL