Show page only to users who have enter an email

Hi, I’m building a page with 3 videos. These videos are tutorials but i wanna show my page only to that who registered your emails in a gravity form. After submitting the form, the visitors will be redirected to the page whit the videos but I want to prevent that somebody with the link of the page have access without a registred email.

I do not want users to have to register username and password.

I dont know the best way to do that. Maybe to use browser cookies?