This article will explain how you can change your InstantSite template.
Scroll down to the Create your website section and click on the InstantSite icon.
Click on the Login button next to the relevant InstantSite package.
Click on the Design link.
Select a colour scheme.
Select a banner using the drop down menu.
Click on the Browse button to select a logo from your local computer, click on the Upload button to add your logo.
Fill in the Site info and click on the Next button.