Creating a floating Enquiry Form Button

Question

Hi,

 

I want to create a floating enquiry button on my website page, since the page is scrolling but the background is constant , i would like to place it on the background, so that anybody is free to enquire , any time the option should be avaliable. Can any body please help me out with that , i am getting no idead from where to start ,  i am stuck up with this, Detailed explanation will be appreciated, thnx in advance.