Follow these steps:
1) Open the Vine app.
2) Choose Profile > Settings.
3) In Settings, specify an email address to associate with your account.
4) After you enter an email address, select the "Reset Password" button.
5) Vine will email the address you entered in step #3 with instructions on how to set your Vine password.
6) After you set your password, return to Vinyet and use the email/password combo you created above to post videos to your Vine account.