You can add People within your Cadence Administrative Site by navigating to your Attendees Menu and selecting "Add People" after clicking the plus sign.
Here you will have a few different ways of adding people to your event:
• Search your previously added people from past events or imports
• Pasting in Email Addresses via the Paste-in Emails option
• Importing via an .XLS template
After adding a new person you will be prompted with two options to either add the person without sending a welcome email, or triggering a welcome email to notify newly added individuals of their access.