1-From your Admin page, click on the icon with the 3 lines (hamburger button ☰) next to View your store, Store configurations>Administrators, click on Create
2-From that page you can add the administrators you want to, and add login information.
3-Click on Create
4-Also you can add all the Administrators Emails you want to your online store by accessing the navigation menu, Store configurations>Emails, click on Create
5-Add the name of the user and their Email then click on Create.