Tstats experts, some help here [Ecobee Installation]

This is my current tstat, I ran the ecobee compatibility and it says in good to go, since I see the white cable laying in the back unused, do I still need to use the power kit?

Also what does the little red piece going from one spot to the other one means

I would suggest if you have any wiring questions to call Ecobee customer service. I had a question when I installed mine & they walked me through wire by wire & stayed on the line through the complete setup & registration. Could not ask for better service.

Thanks @siam I’ll definitely do that now

Honeywell has a good video on what to check for if you don’t have a “C” wire.