With bare copper wires coming from the speakers you will need to attach/solder on RCA male connectors.
Then the male RCA plugs are plugged into two female RCA jacks from a 3.5mm (1/8") stereo plug that goes into the headphone port on the radio.
However, the radio stereo headphone port will probably not have enough power to power the speakers.
So some amplification will be needed
Here is the docking station for sirius radios.
http/shop.siriusxm.com/xm/ctl10600/cp49750/si6676040/cl1/siriusxm_dock__play_home_kit
Note those are all male.
So if your radio is something like this;
http
/shop.siriusxm.com/xm/ctl10600/cp58820/si6462130/cl1/
you could put use the male RCA adapters on the speaker wires directly.
Summary:
1/8" stereo male to 1/8" stereo male cable from Sirius radio to amplifer. Amplifier has red and white female RCA ports. Speakers would plug into those ports.
Making it work will be something along those lines. I used the 1/8" stereo Y adapter to Left and Right RCA connectors years ago to send sound from my PC to stereo.
Here is a link to a variety of RCA connections and wiring diagrams:
https/www.google.com/search?q=RCA+speaker+diagrams&biw=1024&bih=723&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjDneyZqu7KAhVMOj4KHTzOAmcQsAQIGw
However, it mostly depends on how much you can get out of radio itself.