As the Org Admin, you can create new user accounts.
It's easy to create user accounts in Aconex. Each account can span multiple projects, so you need only create one user account for each person in your organization who's working in Aconex. You can only create new users within your own organization.
Note that new users can set their own visibility in the Global Directory when they log in for the first time. To find out more about why they should or shouldn't do this, you can ask them to read Changing your visibility in the Global Directory.
Double-check your spelling of the user's Given name and Family name. If you make an error, it can only be changed by the Aconex Service Desk, so save your new user time by getting their name right.
Do you need to add this user to a project that isn't appearing the list? The Project Administrator has set the invitation mode to "explicit". Ask the Project Administrator to add this user to that project.
If you double-click a project in the Available Projects list, it'll be added to the Selected Projects list. If you double-click a project in the Selected Projects list, it'll be removed from that list.