For Odoo Online:

Odoo Online does not require a port number.

The server url is the instance's domain (e.g. https://mycompany.odoo.com), the database name is the name of the instance (e.g. mycompany).

 The username is the configured user's login as shown by the Change Password screen.

To use XML-RPC on Odoo Online instances, you will need to set a password on the user account you want to use:

• Log in your instance with an administrator account.
• Go to Settings ‣ Users & Companies ‣ Users.
• Click on the user you want to use for XML-RPC access.
• Click on Action and select Change Password.
• Set a New Password value then click Change Password.

Starting from Odoo 14 you can generate api keys.

So instead of password you should use an API key.

To add a key to your account, simply go to your Preferences (or My Profile)

Then open the Account Security tab, and click New API Key.

For localhost:

URL and port is:

http://localhost:8069/

When you start odoo from command line you can see how to access it:

INFO ? odoo.service.server: HTTP service (werkzeug) running on localhost:8069

Default username for localhost is "admin".

The default database for localhost will be something like "odoo16". (if it is on Odoo 16)

For localhost instead of password use a generated API key.

Instance Id - I don't know. Try set it to one -  1

PS: I have created a wordpress plugin that connects to Odoo.

It requires the same data to connect to Odoo API.