Create a page and add an "Inner content" element of type "Form" to it.

For "Action" select "Mode Models", search for "event.event" and select the "Event" one:

Then, start adding the fields you wish your users to fill up - from the "Existing Fields" section(!). The Events Name for example here is just called "Event":

Unless you add a specific field for stage selections or publishing, the event will be created as in stage "New" and can be carried forward by your backoffice staff.

Find more details here:

• https://www.odoo.com/documentation/18.0/applications/websites/website/web_design/building_blocks/dynamic_content.html#form
• https://www.odoo.com/slides/slide/contact-forms-6932