The procedure of creating a new admin user is fully described in the "Muse Console for Application Administration.pdf" document, chapter "Administrative Users Setup and Maintenance".
A particular case of creating a new admin user is if that user must has rights only on one application. Thus, when selecting a grant entry to grant a permission, from the list of available options one must chose "Modify Application". Having only this grant added, then only one application will be available to be selected for administration. In the list of available applications, the new admin user will only see the selected aplication.