Where should I save the Advanced Customization Templates?

Good morning, another few newbee questions:

As per https://devcentral.f5.com/s/articles/Customizing-APM-end-user-login-page-with-APM-Advanced-Customization-Templates, Chapter 4:

1. Download the template-n.zip file and extract all the files from it, where n is the template number.

• Where should I save it?
• How do I assure that this new template applies only to one of my VS? I want to test it first... ;)

Many thanks,

HP.