To customize the Header and the Footer of all your pages, simply login into the WeSupply admin panel and go to:
Design -> Pages -> Page Blocks section-> click on Edit Template for Page Header/Page Footer
Now, on the left-hand side, you'll be able to customize the Header/Footer of your pages and you can start inserting your custom content in this section. On the right-hand side section, you'll see in real-time the Preview of your block content.
When you're done, simply click the Save button.
The same steps apply for the Page Footer customization.