Hello Natalia Jiang,
Thank you for your reply,
No you cannot use the shared mailbox to access the admin center, you need an account with Global admin right or exchange admin, it seem like you have user right so you need your IT department help so they can access the admin center. Only the admin of your organization can access the admin center.
please vote the suggestion it will help the other users in our community. Comments and feedback from our customers really motivate us to perform better and better and provided as much help as possible
I appreciate your kind words.
Have a good day and stay safe
Sincerely,
Eben Ezer Tres | Microsoft Community Moderator