Calling the Computer Literate

Okay, usually if I tinker around long enough on the computer I can figure stuff out. But this whole "HTML" stuff has really got me baffled! I'm trying to add a blog header on my site, but nothing is working! I've tried to upload it from under "Layout" directly from my computer as well as uploading it to Photobucket and getting a code formed. But, nothing seems to work. Tips anyone????