From the dashboard go into the 'Guest and RSVP' tile. There you will find a the 'add guest' button. The first name entered will be the lead guest - if you want to add a partner or group members choose the 'Add a group member or +1' option. Once you have added all members of the party click to save guests and move on to the next guest/group. Alternatively there is an option to bulk upload all guests at the top of the page.