You can elect to send either Detailed invitations --- which include the conference date/time, agenda, and dial-in information --- or Simple calendar requests that invitees can add to their personal Calendar. Choose your preferred type of invitation via the 'Settings' section of your account and hit save.  To access the Settings tab select the Menu tab at the top right hand side of the screen, then click the Settings tab, then choose Meeting Invitations.

The following link will take you directly to this setting within your account if you are already logged in:

    Invitation style FreeConference