This is actually very easy! It requires you to add one line of code to your HTML website page. This code snippet can be found in the Backoffice via "Your own website channel" within the Publication Channels in Questionnaire
An example snippet, so that's everything you need to add to your website, looks like this:
|Code snippet short:|
|Code snippet extended:|
You can put the widget on every page by individually adding the code snippet to those pages.