Here's a flow graph which can be used for broadcasting some content of a Wav file over FM radio frequencies. The original flow graph is from here but it created a lot of missing block errors. So I had to edit it a little bit to make something my own which can be downloaded from here. Since it requires a Wav file, I generated it from a MP3 song file using a tool called Sox as follows.
sudo apt-get install sox
sudo apt-get install libsox-fmt-mp3
sox phillip-phillips-home.mp3 -b 16 phillip-phillips-home.wav
Here's how the flow graph looks in GNURadio Companion tool.