Login to eBay and go to manage my store
 

Under Store Design click on DISPLAY SETTINGS

 Under THEMES And DISPLAY

You want to click on the right hand side of the screen CHANGE TO ANOTHER THEME
 

When you get to the Change Store Theme screen
You want to click on EASILY CUSTOMIZABLE link

You want to click on

CUSTOM HEADER ONLY

It  should be the last option at the bottom of the page.

Click on the SAVE settings button.

When you get back to manage my store

 click on DISPLAY SETTINGS again

Scroll down until you see store header display.

 under STORE HEADER DISPLAY click on YES, Include additional information in the header

This is where you paste in your html for your header. Click on SAVE SETTINGS and you can now go look at your store front.