Navigate to Users → Active users in the left pane.
Choose Add a user.
Enter the Display name and Username. (First name and Last name are optional)
Uncheck "Automatically create password" (if already checked) and provide a password of your choice. Check the box to let the system generate a password for you.
Click on Next.
A service account does not require a license. Hence, select your usage location and Create user without product license radio button.
Click on Next.
Under the Roles option, select Admin center access and choose the required roles (Exchange Admin role is mandatory). Click here to view the list of required roles.