Assigning users to an AWS application

Hello. I'm trying to add a user to an AWS application. I already have other users assigned to the same application.

I'm logged on as the root user, and I've created a new account.

The instructions say:

Choose Applications.

In the list of applications, choose the application name to which you want to assign access.

On the application details page, in the Assigned users section, choose Assign users.

In the Assign users dialog box, enter a user or group name. You can also search users and groups. You can specify multiple users or groups by selecting the applicable accounts as they appear in search results.

I can see my new user in the "USERS" section In this case however, when I select the application, I don't see anywhere to choose "assign users". Please help.