This is a Lightstream Labs feature. For info on enabling Labs features please visit this article
Text files are used to display what you're listening to, recent donations, countdowns, and more!
To add a text file you will need to add the folder that the text file is in. Right click on the Lightstream icon in your system tray, then click on Settings. Once there, hit the link reading "Change". After that, you'll want to navigate to and choose the folder with the text files that you want to add.
(NOTE: This feature is currently only available for Windows. Mac support will come in a future update)
Once you've set your text file folder, you can return to the Lightstream website to add your text files! Once there, you'll want to hit the green "Add Layer" button, select "Text File", and then select the text file that you would like to add!
Want an idea of what text files can be used for? Here's our intro to text files!