This is a really common question people get when they are first starting out with their Twitch Stream because they aren't yet familiar with the Twitch Broadcasting platform.
When you use a program like Xsplit, OBS or any other streaming software you need to have your Twitch Stream Key in order to broadcast to your own channel.
To find your Twitch Stream Key go to www.twitch.tv and find the Dashboard by clicking on your username.
Inside the dashboard (shown below) you'll see “Stream Key” as one of the options, just click on it.
Once you enter the Stream Key tab you will be able to click on “Show Key” to reveal you secret key code. You don't want to share this with anyone as it will allow people to stream directly to your Twitch channel.
If you are worried someone has your Twitch Stream Key you can just click reset key (as shown above) and it will generate a new secret key for you. Update that in your broadcasting software to reflect the changes.