Once you have your invite, click on the link that you received from the organizer (either by email or a link from Facebook or Twitter) to view the details of the exchange, then simply follow the instructions on the page to RSVP. If you have not established an Elfster account, you will need to create one to RSVP. Multiple accounts may use the same email address, however, each person needs to have their own unique user name and password for their account.