When you get Business Central in your hands for the first time, only one user is defined in the system. It is up to you to create new users and assign them appropriate permissions.
There are a few things to keep in mind when creating users.
The user must exist as a user in the tenant (visible in the Admin Center)
There must be an available license for the user in Business Central
The user must be uploaded to Business Central when points 1 and 2 have been completed
User permissions must be defined on the User Card.
In order to add users to Business Central, the user must be assigned a license. Start by creating the new user in the Microsoft 365 Admin Center (see method 1 here below) or as Wisefish to assign the license for you (see method 2 below for details). If no license is available for assignment to the user, contact Wisefish through support@wisefish.com.
First you need to make sure that the user exists in the tenant. If a user exists in the tenant, the new license must be assigned to him, this is done in the Microsoft 365 Admin Center.
If the user needs to be created from scratch, follow the instructions of Method 1 here below.