Adding Pages is most easily done from the tool bar at page top when you sign in (you choice shown is "Edit" or "Add Page"). You'll be able to select page type, name it, and add attributes from the window that opens. This page should automatically populate the Nav menu unless you tic the "exclude from nav" option. Adding pages from other than the Main will create sub or child pages on the tree (looking at your sitemap will illustrate this)

Customization of the page for color can be best edited on the main css file (background of the individual blocks can be applied by clicking on the block to edit and choosing "design" instead of edit)

Footer edits can be done in the Footer file found in the themes Elements folder