Convert existing header into an editable header

I am very new to Sitefinity and am totally lost.

I have a master page that has a user control (.ascx) header. The client wants to be able to edit the html of this header in Sitefinity and has requested that i convert this header into an editable control in Sitefinity. Where do i begin? I have looked at the Hello World tutorial but cannot see how that would apply to this need. The existing header has a search box in it that has code in the code behind for the user control and the user control header also has another user control dropped into it which is making this task very difficult for me to wrap my head around.

Any help would be much appreciated. Thank you.