Hi Alfredo
You just have to visit the page you have added the Lead Generator shortcode [immonex-lead-generator]
to in the website frontend. Here, select a property type and then click yourself through the given form pages. On the last page, enter your own email address and submit the data. You will then receive a submission confirmation mail as well as an admin notification if your mail address is also the site’s admin address or stated as recipient address in the plugin configuration (email tab).
(Of course, the WordPress installation itself must be able to send mails.)