Hi i can not add departments

Hello there, Falik,

If you're referring to class or location tracking, this feature is only available in QuickBooks Plus. If you're subscribed with that subscription, follow the steps below:

1. Click the Gear icon.
2. Select Account and Settings.
3. Select Advanced. Then select the Categories section to edit.
4. Check Track classes.
5. Check Warn me when a transaction isn’t assigned a class. This is optional, but it's good to turn on so when you look at reports, you know everything got classified.
6. Under Assign classes select One to entire transaction or One to each row in transaction.
7. Select Save, then Done.

Check out this article for more information: Get started with class tracking in QuickBooks Online.

I'll be right here if you need further assistance.