Joomla4 : how to set parameters in an extension?

Question

I have developed a Joomla3 extension and I try to run in in Joomla4.1

In my XML file:

<extension version="3.1" type="plugin" group="content" method="upgrade">

<config>
    <fields name="params">
        <fieldset name="basic">
            <field name="webmasterid" type="text" default="" label="Enter webmasterid"/>
            <field name="password" type="password" default="" label="Enter Password"/>
        </fieldset>
    </fields>
</config>

But I don't see any way from my /administrator/ panel where I can set these 2 params: webmasterid, password

What is the correct way to have them displayed in /administrator/ panel ?

(the plugin still works correctly, but I have to set these values directly in my plugin code)