How to edit internal html code?

I want to design a contact form in Wix and add the contact to my aWeber list.
aWeber has an option to do this. They have given an HTML code to add to my custom form created in Wix.
https://help.aweber.com/hc/en-us/articles/204027896-Can-I-use-my-own-form-

My question is, where do I add this HTML code?

Put the html code inside a html iframe on your page.
https://support.wix.com/en/article/adding-html-code