When you are using my template code,then no need to add a header. everything in my code.
But, when you are going to use my Header image alone, follow the instructions,
1. Save the Header image to your computer.(mostly header images are in tinypic).
2.Go to blogger layout, then Page Elements, then click edit as shown below
6.Then select Instead of title and description.
Note: After Saving the header image to your computer you can modify it with some fonts, to write your captions like,