When I use the turn signal dash lights blink and dim and radio goes out. What could be the issue

Start by removing and fully charging the battery--most auto parts stores will do this for free. Clean the battery terminals, cable connections, and all grounds. Clean both ends of the wire going from the alternator to the battery. Finally, have your alternator tested--the regulated battery voltage across the battery terminals, while the engine is idling, should be 14 to 15 volts. I suspect the alternator may be bad (brushes worn down too far).