Banner Header

Assalam Walaikum/ Hello,

I'm new to blogspot although it says I've had a profile since 2008..Weird. I've spent the majority of  my time since I started this blogging trying to put up a banner as a header. I need to use a html code and I thought I knew how but apparently I don't. So, my first post to this blog is to ask for help. Please if you're reading this and know how to put a banner up as a header using a html code, send some suggestions. They will deeply apreciated. Thanks.