To CUSTOMISE a ready-made header:
Left-click to bring the header up to the full size
Right-click to save the header to your own computer
RECTANGULAR HEADER - SQUARE OR OBLONG
Open in a graphics programme.
Add a text layer on top - any fancy lettering you want (there's loads of free font sites listed on Computery, or else google for free fonts) and then flatten the layers. Crop if you need to.
Save as a jpg, then go into Header in Layout, and browse for your header.
Tick the Instead of Title & Description box, and upload.
This could be an oval, or have a scallop or lace edge edge etc, and will have been created on a transparent background.
Create a text layer, type in whatever you want, then MERGE the background layer. Don’t flatten it, or the background will go solid white just like a jpg. Don't know why, but it does.
Loading a png image directly to your blog from your computer often seems to do this – again, I don’t know why (and it doesn’t happen every time) but it does happen. If you have a white background anyway, it doesn’t matter – but it can look really awful if you have a dark or patterned background.
Hence you need to host your header on Photobucket to keep the transparency around the image:
To do this, open a free account with www.photobucket.com and adjust the upload sizing of the files. You need to copy&paste the [IMG] code (remove both [IMG] and [/IMG] codes) into the header box.
Tick the Instead of Title & Description box and upload.
You might want to remove the borders around the header - or make them thicker... If so, read this tutorial.
You also might need to move the header over a little - it can sometimes throw to the right (a Blogger thing, to do with their default header margins) or even move the entire header down a little - another easy fix! Just read my tutorial which will tell you how to position your header exactly where you want it.