3 way Dimmer switch, Add on switch and lights

I am new to HA running it on a green. I have installed several switches and other accessories both Zwave and Zigbee BUT I had never installed a 3 way switch (SMART) NOR one which is a dimmer till now and have some questions. Hooked the switch up and NOTHING, powered up and loaded into HA but not functioning remotely or manually.

  1. what is an add on switch ? I have looked at descriptions but they are vague and they are cheap, seems just like a dumb switch nothing much than just a switch how do they differ and can I use the original switch along with my smart dimmer? Says no special add on switch needed in the description.

  2. Using a ZOOZ Smart Dimmer switch, and I don’t have florescent lights, not sure exactly WHAT they are here is what I am using, they plug and turn thought they were halogen, small and bright. Not a big deal, will go to lowes tomorrow and change out the fixture over the bed to LED anyway.

https://www.amazon.com/dp/B09482M85Y?ref=ppx_yo2ov_dt_b_fed_asin_title