Are you using the Desktop program installed on your computer? It looks like you are posting from the Online version.
In the Desktop program go up to File-New. It will first ask you to save the current open return.
For Online......
Online is only good for 1 return per account. But you can use the same email address for 5 accounts. How to start another return in the Online version
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596