You have the user in Microsoft Entra Users which sync the users from your on-premises user.
You will assign Teams license you own to one users via manual operation.
Step
Go to M365 Admin Center.
Go to Users – Active Users.
Select the user who will have the license assigned. Click it.
At the User detail being popped up, Select “Licenses and apps” tab.
Confirm the license is available. (If no license count available, if you assign the app to the user, new license will be purchased in background. Becareful.)
