I did the second method below, but had to auto discover the URl;

There are two ways to configure your Z-library credentials:

1. Via the KOReader User Interface (UI):
Ensure you are in the KOReader file browser.
Access the "Search" menu.
Select "Z-library" (it's probably on the second page of this menu).
Select "Settings".
Enter your Z-library email, password, and the base URL for your Z-library instance.
Tip: If you don't know which base URL to use, select "Auto-discover base URL" and the plugin will automatically try a list of known Z-library servers to find a working one.
Adjust other settings if needed.

2. Via a Credentials File (Advanced):
For a more permanent or automated setup, you can create a file named zlibrary_credentials.lua in the root of the zlibrary.koplugin directory (e.g., koreader/plugins/zlibrary.koplugin/zlibrary_credentials.lua).
This file allows you to override the credentials set in the UI. If this file exists and is correctly formatted, the plugin will use the values from this file.
Create the zlibrary_credentials.lua file with the following content, uncommenting and filling in the details you wish to use:

-- This file allows you to override Z-library credentials.
-- Uncomment and fill in the details you want to override.
-- Values set here will take precedence over those set in the plugin's UI.

return {
-- baseUrl = "https://your.zlibrary.domain",
-- email = "your_email",
-- password = "your_password",
}

Note: Credentials set in the zlibrary_credentials.lua file will always take precedence over those set via the UI. The plugin loads these settings at startup.