You can add endpoint in 4 steps:
Step 1 - Click on "RTB" in left menu-bar
Step 2 - Click on "+" near RTB Endpoints in main window
Step 3 - type specific name in "Name of the endpoint", paste endpoint URL (don't forget to use http:// or https://) to "Endpoint URL" field, setup settings such as GEO, websites, Ad placement and traffic type.
Step 4 - Push "Create endpoint" button
Your endpoint created and pending for moderation.
You can find your endpoints in "RTB" to manage your endpoints.