Congratulations on getting started with your Network account! You can begin by adding accounts, as detailed in this article.
Once you've created an account, you'll need to add display groups to it. To get started, click the Displays dropdown, then the "Add display group" link, as shown below:
You will be taken to the usual Add Display Group page, with one exception: the option to choose which account you'd like to add it to. Click this Account dropdown to search and select the account you'd like to add this display group to.
Next, you'll be prompted to add a setup phrase, name the display group, and go through the usual process of adding the display. You can read more about that in this article.