Fixed Button Sidebar With Contact form 7

Dear Experts,

I am using Contact form 7 for one of my project. But need same behaviour which is below demo link provided. If you see right sidebar one help green button fixed. On click on this there are pop up form open. I need exactly this one. Any body know how to achieve this.

Demo Ex: https://www.linium.com/services/planning-in-the-cloud

Thanks