how to use my system

First, factory reset any Sonos units you have: 

https://support.sonos.com/en-us/article/reset-your-sonos-product

Since you have a Connect:Amp, it can be S1 only or S1/S2 capable.  So on your phone, download the S1 app for Sonos.

Then, setup a new S1 system:  

https://support.sonos.com/en-us/article/set-up-a-separate-sonos-s1-system

If the Connect:Amp is S2 capable, you will be prompted to upgrade.

Also, what will be your source of content? Online music? CD’s? Local music files? Bluetooth? AirPlay? Do you expect to be adding a TV soundbar?

Both Android (Google) and iOS (Apple) have removed the ability for Sonos (and others) from using their devices as hard drives for playing music, which Sonos (and others) used to use. As I suspect you’ve surmised, Bluetooth is a good method (although bandwidth limited) to use a player on the device to access the music, and send it to another device. But given the age of the CONNECT:AMP, it is unlikely it has electronics in it to accept a Bluetooth signal, although there could be something that is attached to the Line In on it that does. Hard to tell. 

Your best bet is to move this music to a computer’s hard drive, or an NAS, both places Sonos would have access to. 

Thank you all for your quick and very helpful responses.  As suggested, I downloaded the S1 app, connected the amp via ethernet cable to my router and was good to go….  

Simple once you advised me.

Sometimes, the ‘simple’ isn’t always obvious to us… ;)