For this:
Register on QForm and add your website
Switch to the design mode, add and configure the field types:
Place the Text block . The field supports HTML tags, using which you can add elements and set styles inside tags
Go to the Embed Code tab
Copy the DIV to install the form and the script to call it, paste it on the site
After installing the code, a button will appear on the page that opens the form in a modal window