In most WordPress themes, the sidebar and footer are so called widget areas. This means that you can use the dedicated “Mailchimp for WP Form” widget to show a sign-up form in these areas.

To add this widget to your sidebar, go to Appearance > Widgets and select the Mailchimp for WP Form widget. Then, drag it to one of the available widget areas.

Mailchimp Sign-Up Widget

Select the form you would like to show and visit your site. Your form should now show in the widget area you selected.