The OPC server you want to use can be downloaded from the following address.

https://www.faweb.net/en/download/download/

The software name is "[DEMO] DeviceXPlorer OPC Server V7" and supports "64bit" and "32bit".
The one I used is for 64 bit.

A demo version is available and is free to use.

After installing the software, you can use the OPC server by the following operations.

(1) Click「Tool」→「Option」
(2) Click the "..." button of "OPC UA Server Setting" in the displayed window.
(3) When the "OPC UA Server Setting" screen opens, check "Enable OPC UA Server".
(4) Uncheck "Enable Anonymous".
(5) Click the "OK" button.
(6) Click “Tool” → “User Management” → “Configuration”.
(7) The "User authority" window opens. Set the user name and password and click "OK".
(8) Click “Tool” → “User Management” → “Login” to log in to the user created in (7).

(9) Go to Unity.
(10) Set the "user name" and "password" set in (7) to the "user name" and "password" of the "OPCUA_Interface" component.
(11) Set the "Port No." displayed in the "OPC UA Server Setting" window.
(12) It is assumed that the OPCUA server and Unity are running on the same PC, so set the IP to "localhost".
(13) Click the "Import nodes" button of the "OPCUA_Interface" component.

After doing the above, an error will be displayed in the Unity console.

I want to communicate with this OPCUA server using username and password, please help.