Old fashion MS Win, API key procedure

Hello [this is my first Q in here, and I am using a MS Win10 machine, with HTML/FTP-approach]

I want to use the GitHub examples as of https://github.com/graphhopper/directions-api-js-client

While uploading this on my own website, I don’t know where to place my nely created key in order to (get verified access) use the Graphhopper engine?

1st try in the index.html [line 28]:

   <div id="enter_key">
                    <img id="custom_key_enabled" class="hide" src="img/included.png" alt="using custom API key"/>
                    <input id="custom_key_input" placeholder="[MY NEW/OWN KEY?]"/>
                    <button id="custom_key_button">Set</button>

2nd try in demo.js [line 37]:

var defaultKey = “[MY NEW/OWN KEY?]”;

Neither works?

// br … and; on before thanks