Upload a Custom Store Theme
Sign in to your eBay seller account.
Click My eBay at the top of the page.
On the summary page, click Manage My Store. Next, click Edit Store
You can edit your billboard and logo here. A billboard must be 1200 by 270 pixels. Logos must be 300 by 300 pixels.
Scroll down and select 1 Text Section / HTML from the drop-down menu and click Continue.
Type a title for your custom storefront in the Page Title field.
Click the Enter Your Own HTML tab in Text Section 1 and copy the HTML code for your custom store template and paste it into the text field.
Click Hide Left Navigation Bar if your custom theme does not use the left navigation bar or Show Left Navigation Bar if it does and click Continue.
Click Save and Publish on the preview page. eBay directs you to the Custom Pages summary page.
Scroll down and click the drop-down menu under Store Homepage and click the name of the custom store you uploaded, then click Apply to use the store template.
Upload Custom Header
Log in to your eBay seller account.
Click My eBay then Manage My Store then Display Settings.
Click Change to Another Theme under Theme and Display and click Easily Customizable under Themes.
Click Custom Header Only then Save Settings to return to the Display Settings page.
Click Change in the Store Header Display section and click Yes, include additional information in the header.
Enter the HTML code for your custom header in the text field. If you purchased a custom theme and header, the code for the header was most likely emailed to you in a separate file.
Click Save Settings.