To let contacts from your database know about your event, you can invite them (either individually or via contact lists) by creating an Invite on the 'Emails' page. When you invite people directly from Seatrobot, they receive an invite email with 'Confirm / Decline' buttons and their own personalized Registration page. They do not have to fill in their personal information to be registered. When they accept your invite they automatically show up as confirmed in your Guest List.
If you want your contacts to be able to promote your event to other people you don't know, use the event's Register Page. Copy the URL from your Setup page, or from the Dashboard and include them in emails, on your website, Facebook page etc.
From your Dashboard you can also toggle your event ON to appear on your public Events Website: this website displays all the events you toggle ON and has a fixed web address you can add as a link / page in your company website, Facebook page, Instagram bio etc.