How can I add another user to my business office 365 I have?

In one of the programs click the program name in the menu bar & select the About... listing to determine the specific type of license. This may help:

https://www.microsoft.com/en-in/microsoft-365/microsoft-365-business#plans

To see what Microsoft 365 license is in use and whether another user can be added, two things are needed: identify the subscription type and then, if it is a business subscription and there is admin access, add the user and assign a license.

1. To identify the license

• Sign in to the Microsoft 365 account in a browser and go to the account’s services and subscriptions page. The subscription name there (for example, Microsoft 365 Business Standard, Microsoft 365 E3, Microsoft 365 Personal, etc.) determines whether it is a business or personal plan.
• For Outlook for Mac specifically, only certain licenses include rights to the desktop apps such as Outlook, Word, Excel, and PowerPoint. These include:
  • Home (personal): Microsoft 365 Personal, Microsoft 365 Family
  • Work or school (business/enterprise): Microsoft 365 Business Standard, Microsoft 365 Business Premium, Microsoft 365 Apps for business, Office 365 E3/E5, Microsoft 365 E3/E5, and similar education/government plans. If the subscription is Microsoft 365 Basic or another plan that does not include desktop apps, it will not allow installing or activating the full Mac apps.

2. Whether another user can be added

• Personal plans (for example, Microsoft 365 Personal) are for one person and do not allow adding additional users in an admin center.
• Family plans allow sharing with multiple people, but that is consumer sharing, not adding users in a business tenant.
• Business plans (for example, Microsoft 365 Business Standard, Microsoft 365 E3/E5) support multiple users, but adding users requires an admin account and enough purchased licenses.

3. How to add another user in a Microsoft 365 business subscription If the subscription is a business plan and there is admin access:

• Go to the Microsoft 365 admin center at https://go.microsoft.com/fwlink/p/?linkid=2024339 and sign in with admin credentials.
• In the left navigation, go to Users > Active users.
• Select Add user.
• Enter the new user’s information (name, username, etc.).
• During the add-user flow, assign a license if one is available, or choose Buy license and add user to purchase and assign a new license at the same time.
• Complete the wizard. After finishing, the system can send the new user’s sign-in information to up to five email addresses.

If multiple users need to be added at once in a business tenant, use Add multiple users under Users > Active users in the admin center and either enter users in the grid or upload a CSV file, then assign licenses to all of them in one step.

If there is no admin access (for example, the account is part of an organization managed by someone else), only that organization’s administrator can add users and assign licenses.

References:

• Add more users and licenses
• Add users and assign licenses in Microsoft 365
• Set up Microsoft 365 apps for business
• How licensing and access works in Outlook for Mac