You can create a sub-account in the Accounts section.
To create a sub-account:
Click the Create sub-account button on the right side of the screen.
In the popup window, name the sub-account.
Add the description for the sub-account optionally.
Enter the amount you want to transfer to the sub-account.
From the dropdown list, choose the source from where you want to transfer the amount to the sub-account. It can be your Primary account or another sub-account.
Click the Create sub-account button.
Once the new sub-account is created, you can create budgets inside of it, cards, and invoices and spend freely, just like in your primary account.