Here I will try to help out people who want to get started or are looking for different software / service's to use for DJing in 3DXChat. I will try keep this short and sweet (trying to keep it simple too) or I could go on forever!
There are many different products you can use to get the job done so I will only list some of the very popular options below.
The DJ software is what will play your music on your computer, you can play the music directly in the software or you can plug in controllers to play. The bottom two options (Mixxx and Winamp) are both freeware and will not cost you anything to use, the more powerful software with more features will require you to pay to use them. If all you want to do is just stream music and not mix then Winamp is the one for you, it's very simple and easy to setup. For anybody looking to go further into DJing with mixing, personally I would always tell people to stay away from Winamp as it offers no features at all that will enable you to progress with DJing (it will only play your music song by song). A good starting point for anybody looking to mix would be to pick up Mixxx as it's free and let's you mix your music using it's various features. Then if you're looking to go a step further again you can look at the paid software, they all work pretty similar but with minor differences between them, you can pick up free trials to test them out before buying on their respective websites. Go ahead and try them out, find the one you prefer before spending your money!
Setting up your streaming service will be the next step you need to take after you've got your DJ software. Above are a couple of the most popular services to use, they supply free servers you could test with and have some fun but the more slots for people to listen at the same time and the higher quality of stream comes with a price. Personally I have been using SHOUTca.st's Pro option for the past year and I have not had a single problem with it, they offer an amazingly high quality service (but that's just my opinion). At the end of the day you only need to pay for what you need. Once you have your server set up you will then need to connect your DJ software to it and then use the link your server will provide you and paste it into 3DXChat. With everything hooked up correctly you should be ready to go, start playing that music to your hearts content!
If anybody has any further questions with anything then feel free to ask, I will try my best to help you out.