Blocksy has a built in MailChimp extension that will help you to gather your subscribers in a MailChimp list through a sidebar widget or a module that sits at the end of each post.
In order to activate the MailChimp extension, go to WordPress Dashboard → Blocksy → Extensions and click the Activate button on the MailChimp extension.
API Key and List ID
After you activated the extension you have to connect it with your MailChimp account and select the List ID. More info on how to generate an API Key can be fond here.
After you generated the API Key – click on the little gear icon (example below) and a popup window will appear, insert the API Key in the desired field and after that select the List ID.
After activating the MailChimp extension, go to Appearance → Widgets and you will find the MailChimp widget in the Available Widgets list. You can place it inside any available widget area.
Go to Customizer → Post Types → Single Posts scroll down to Post Elements → Subscribe Form and make sure it is turned on.
Now that you have enabled the MailChimp Subscribe Form module, you will have access to a set of options that will help you to set it up and customize to your needs.