How do you get a free stereo on free realms

Okay well, if you mean a "boom box" You will need to buy SC in real life. ($1 per 100 SC) The boom boxes are usually around 200 SC so if you really think about it you are spending $2 on a online game for a boom box. IF you are talking about a actual stereo, you can also buy those with SC or go to your profile and this little thing changes every once in a while. Just refresh and it will show up.
If you did that it would be free. The thing will be a yellow rectangle with a picture then you will have to go through a little advertisement. No info required. Its free that way. Also, you can find your boom box in your belt, and a stereo can only go in your home.