Just adding my 2 cents worth. It's always bad to cut into an original car harness unless absolutely necessary (read never). This just creates hidden/ hard to diagnose wiring issues later when wiring re-connections aren't made properly and fuses start popping, or things work intermittently.
With that said, I'd start by re-connecting the harness wires you've already cut into. Make good solid connections and then solder the connections back together. Cover the spliced/soldered connections with heat shrink tubing or electrical tape so that none of the connections come into contact with other bare wires. Next get an adapter harness for your radio that plugs into your car harness and then adapt it to the radio using the adapter instructions.