Go your Manage event > Special pages > Speakers. Type the speaker's name and see if s/he appears from the extensive database of speakers with existing Conferize profiles. If the speaker does not appear, click "Create new" and add the information.
When a speaker is added, s/he is presented on your event website on the Speakers page. Adding a speaker also enables you to add the speaker to a session card in your Schedule.
When adding a new speaker you can also invite the speaker to become an active member of your event community with an email invitation.