The extension plugin will place a simple subscribe checkbox with a label of your choice on the booking form of the Events Manager plugin. The customer can then tick/check this checkbox to subscribe. You have control over whether the checkbox should be auto/pre checked and which mailing list(s) the customers should be subscribed to.
View the installation and set-up documentation for details.
Features of this WordPress Newsletter Plugin Extension
Install this as an extension plugin to the Newsletter plugin which can be easily turned on or off according to your needs.
Configure the newsletter checkbox by specifying a custom title, auto checking it, choosing the list(s) that users will be subscribed to in the WordPress Newsletter plugin.
The newsletters subscribe checkbox appears on the booking form as you configure it on the front. As your users fill in the form and check the checkbox, they will be subscribed.