Side navigation solution?

Hi all,

I am moving a website over to square space (template 7.1), this is the website I am moving: http://www.allconstruct.com.au/. I am needing side navigation on some pages (top and side nav) example here; http://www.allconstruct.com.au/highgate-hill-design-build

Is there a solution for this in square-space 7.1? I don't mind attempting either:

1. Coding this in to the template direct.
2. Adding a solution via the code injection tool or custom CSS sections
3. other?

Side navigation really helps with with website for large civil contracting companies.

Please note: I created all the fly-out and side navigation on the example website by coding the template directly.... but I understand you can't do this in 7.1, is that correct?

Thanks you in advance.

Regards,
Tonga.