If you haven't purchased Wondershare UniConverter, you can sign up for a new account to use. You'll see the Create a new account button on the interface after clicking the Log In button in the right-top corner.
Then you can see a new interface to ask you to input the email and password, finish the asked information and click on the Sign-Up button to sign in.
Tips: See what you can do at Wondershare Account Center.
https://videoconverter.wondershare.com/guide/#n1.4