making header image a image map

To do that you need to do some HTML editing. The header image is most likely output by the header.php file in your theme, so that’s where I’d start looking for it.

When you find it you need to add in some HTML code to set the image map details to that image. There’s some good info here:

https://en.wikipedia.org/wiki/Image_map#Definition_in_HTML

And a more in-depth look at it:

https://www.javascriptkit.com/howto/imagemap.shtml