When accessing Journey Optimizer for the first time, you are provisioned a production sandbox and allocated a certain number of IPs depending on your contract.
To be able to create your journeys and send messages, you need to go though the configuration steps listed in this documentation: Get started with Journey Optimizer Configuration
Please feel free to reach out for your queries through the Community Q&A or below comment section. If you have any feedback or feature requests for the Adobe Journey Optimizer product, then submit them here.
Sukrity Wadhwa