How to add Coding about HTML in Header part?


Hello Guys ! I have some trouble about Coding in my landing page

My company have website is call “Minerva” It’s website about when Customer fill information and information will show in this website (e.g. Name , Address , Tel.)

And I must put coding about this website in Unbounce. I have old Landing Page form Instapage website. I put code in HTML(Header) part. But in Unbounce I put it in Javascipt isn’t work(Error) and CSS too because HTML in Unbounce is just a box I want HTML part like Javascript What should I do ?

Thank you for your help ! I tried to use Unbounce to develop my Landing page ! : )