You may invite people to your event from the event page itself. In the top right hand corner, click on "Invite friends".
You can add a few people at a time, or if you need to add lots of people at once or import an email list, "Add in Bulk" tab where you can add many email addresses at a time, just separate them by commas, semi colons, or put each email address on a new line.
Each person you invite will receive an invitation to the event. You may customize the invitation that they receive from the Event Control Center for your event on the "Edit Invitation Template" underneath the "Invitees" section.