As far as I know, you cannot directly embed the signup form that pops up into your website (and it is not considered safe to use signup iframes on some browsers) Instead you can build your signup page in HTML + CSS and add the attribute level connectors so that your custom signup form 'talks' to the memberstack API. Here is the official video in how to do this https://youtu.be/ji_xsZ5pBOs
Maybe @memberstack will make an updated one with more detailed use cases?
