Hi Julien,
Thank you for your purchase and welcome back to the premium plugin support forums! If you have the ‘Allow anonymous submissions‘ option unchecked in Events > Settings > Community (see screenshot below), users will be required to log in prior to submitting events.

If you would like users to log in before allowing them to add events, my recommendation would be to add a registration form somewhere on your site, then add a link to your Submit Event form on their account page or wherever you feel is best.
You might also want to add a link from your Submit Event form to your site’s registration page. It might also be a good idea to include a note on the Submit Event form along the lines of, “You must log in/register before adding events.” Check out Theme My Login to gain more power over your site’s login/register forms.
I hope this helps clarify how the plugin works and let me know if you have any more questions. Thanks again and take care!