How do I create a new form in a shared account?

I have a basic account, but I have been added to another premium account that has far fewer limitations. I can view and edit existing forms in that account that has been shared with me... but how to I create new form in that account?

You may click on the shared folder and the create form button: 

If the form is still created in your account you may drag and drop it to the shared folder, this will move the form from your account to the main one. 

I hope this helps.