when i have the converters, do they give me the negative and positive range for the audio wave
No.
Or i have to trick them out with a resistive voltage divider and a capacitor?
Yes.
it works but i don't know how to get the values and send it back to the other arduino
The values you need to send to the other arduino are the values that you send to the PWM channels.
Do you know if your transmitter can handle the bandwidth that you need?