Create a Mailchimp Email Template that i can edit the text and images

I need to create an Email Template on Mailchimp.
I want to be able to edit, subject fileds, content, images
Our website is connected to hubspot.
We have a Request For Demo landing page on our website that is connected via hubspot, so all new leads go through to the hubspot CRM

We need our Email Mailchimp Campaigns that have a Call To action to also connect to hubspot - so all new contacts are registered on the hubspot CRM

I have examples of ones that we produce on hubspot, plus i had design ideas that i want to add to the mail chimp