Why does my iPhone 3GS say No Content when I open iPod?

My sister gave me her iPhone when she upgraded, but I can't seem to open my music. I have tried syncing, resyncing, soft reset, resetting all settings and nothing seems to work!

When your iTunes is open, go to the DEVICES tab. It should be on the right side. Should say your devices name, for example, NARNTEK'S iPhone.1 click on the devices name. Make sure it goes to the specifications on your phone, showing you how much memory you have left, etc. Click on the music tab. Make sure the sync music option is check-marked. If it isn't then you are not going to be able to get to your music.