are you asking how i get standard FM radio since i ditched the factory radio in favor of a tablet? if so, i don't! i absolutely hate FM radio, and even XM/Sirius - way too many commercials. in town i listen to Pandora streaming over 4G and in remote areas i listen to MP3z ... unless i'm on the trail - then i listen to the sound of tires meeting sand and rocks usually!
some folks with tablet based carputers use a DVB-T stick such as this to get FM radio:
http://www.amazon.com/NooElec-RTL-SDR-RTL2832U-Software-Packages/dp/B008S7AVTC
with an app like one of these:
https://play.google.com/store/apps/details?id=de.ses.wavesink&hl=en
https://play.google.com/store/apps/details?id=marto.androsdr2&hl=en
those little sticks were designed as a digital tv receiver for certain areas (i believe some european countries), but hackers soon found out that it could work as a cheap SDR (software defined radio) device.
the simplest answer is to keep the factory radio and add an aftermarket auxiliary input to it to route audio from the tablet when needed. i just skipped all that since i personally had no use for the factory radio.