After using the Static Site Import, your Head, Header and Footer scripts are already within your Pages. It is worth noting that some Sites use one Template for every Page, whereas others will use different Templates throughout their Site.
For each of your these scripts, you'll need to create a header, create a head (if you'd like to), and create a footer. Simply cut and paste your headers, heads and footers from your Pages into the relevant place.
Once you have done this, you can create a template.
When editing your Template, you can use Toolbox on the right-hand-side to easily output the liquid required for your Code Snippets, Header & Footer.
Content for Layout
When a Page uses this Page Template, the {{ content_for_layout }} liquid tag shows exactly where the Page content should be outputted inside the template.