Connect speakers


So im new to the speakers world and I just received two big speakers from my uncle. There not Bluetooth. I was wondering how could I connect them together and then play music from my phone to them using Bluetooth. They are TR6 Event speakers. I heard about chromecast but I do not exactly know how it works and if I need to by two one for each speaker. So I would like to know:
1- What cable do I need to buy to connect them together.
2- How can I play music to them using chromecast.