I'm not with Mailchimp, but the process is similar to other providers.

Have Mailchimp generate HTML code, copy it and then paste it into an HTML object on WebSite X5.

If it should be in the footer, then under point ...

2 Template > Contents of the template / footer

... drag an Html object into the footer area and paste the previously copied HTML code there.

Now place the Html object correctly and test it in all 4 resolutions in the preview.

>>>The required HTML code can be found here at Mailchimp, see

----- Mailchimp website -----

Add an Embedded Signup Form to Your Website

Section > Generate embedded form code

Copy Code, see screenshot

7. Paste the code into your website where you want the form to appear.

>> https://mailchimp.com/en/help/add-a-signup-form-to-your-website/

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In a similar way (there is a code that you paste into an HTML object on WebSite X5), the previous newsletters can be installed as a list of links on the website, see

>> https://mailchimp.com/en/help/add-an-email-campaign-archive-to-your-website/

Many thanks for the pointers. I have signed up to Mailchimp so will see how I get on.