How to Embed Forms on a Website
This is the preferred way to embed forms. You can get the embed code of your form by clicking on Embed / Share on the top-right corner, on the form edit page.
The embed code for inline forms is one block of code which you would copy and paste on your page, where you want the form to appear.
Popup forms have a two-part embed code. The first part can be inserted anywhere on the page (but preferably towards the end) and the second part is the link which triggers the form, and should be inserted where you want the link to appear.
If you look at the first part of the embed code, it has a unique embed ID - htwpp. This ID is then used in the popup link, as an attribute - data-fc-open='htwpp'. If you want to trigger the popup form using a custom element on your page, you would use this attribute on that element: data-fc-open='htwpp'.
Method Two: iFrame
The downside to using iframe codes is that it disables certain form features like redirect, auto-height, etc ...