How do I copy my tree to another account

I began my genealogy to 01/10/2009 , but at the time did not realize the extent of my family , because there was a 
family branch of my maternal grandfather that I was completely unaware . By researching and entering the data of 
the family Vieira saw that they were too many. I wonder how can I copy my tree to another account to create
( vieiragrande family ) which will only appear family Vieira and family .