I want to add my facebook and twitter on my store
how I can change them?
You can check how to manage HTML blocks here:
http://www.abantecart.com/ecommerce-documentation/85-admin-user-manual/design/blocks-user-manual/html-block
You can get extension:
http://marketplace.abantecart.com/index.php?rt=product/search&keyword=facebook&category_id=0